Comparing myself with my BF's exes (long post, need perspective)

I'm very sorry about the long-winded ramble (I put a TL;DR ("too long; didn't read") at the end), but thank you to whoever takes the time to read any or all of what I needed to get off my chest. I feel my judgement is clouded by emotion, and I am having a difficult time distinguishing between what is rational and what is not... any advice or clarity is appreciated. My boyfriend (31M) and I (30F) met at work a year before we started dating (restaurant: he worked kitchen, I worked front of house). From the beginning it was obvious he liked me. Around 6 months in I started liking him too, but we didn't start dating until I found a new job, and he has since found a new job too. We've been in the relationship for 1.5 years now, and in June he moved into my apartment (he initiated it). Overall I feel we get along great and have a strong relationship, however for the past several months I've struggled with new-found self esteem issues and would like some perspective from others. I say "new-found" because prior to this, I was pretty confident with who I was. I know I'm not the most beautiful woman in the world or anything, but I felt attractive nonetheless and that I had a lot to offer. The last time I struggled with self esteem was in my first LTR when I was ~20, where a year into dating, my then-BF confessed he had a thing for Asian women (I'm white) and wanted to have sex with one. Young and naive, I reluctantly said okay, thinking it was something he needed to get out of his system. We dated for another year, during which I felt so inadequate and distrustful that I snooped through his computer and found hurtful evidence that he was unfaithful on multiple occasions (not just with Asians) and an excellent liar too. ------ Between that first LTR and my current one, I've had two other positive LTRs that both ended on good terms, neither of which did I experience feelings of distrust or self-consciousness. I believe my new insecurities may stem from two things my current BF said on our first date - things which didn't bother me initially. The first thing was when a coworker's name came up in conversation (his friend who also worked in the kitchen). Apparently this friend made fun of my BF for liking me, to the point that they got into fights about it. He even told me this friend texted him a photo of one of his exes who is a model he dated for ~3 months in 2013, followed by the comment "what happened to the old you", to which my BF replied "I'm still here and she's a gold digger". The fact that my BF stood up for me throughout meant a lot, and I was so secure with myself at the time that I didn't compare myself with this model, even if his immature friend blatantly did. Second thing: We ended the night with conversations that lasted until sunrise. He talked about what he wanted in life and in a relationship, but at one point he brought up a different ex (let's call her "X2") from 2014 whom he dated on and off for ~8 months but broke up with because she was obsessed with another man (whom she later married). My memory's foggy why he even brought her up, but when he found out I wanted the same things in life as he, he seemed happy and said "good, because otherwise I'd have to go and get her back because I can't resist her". Considering him and I liked each other a lot at this point, I didn't take this comment very seriously. ------ So we continued dating and our feelings got stronger until we were both very much in love. X2 didn't cross my mind except on a couple occasions when he scrolled through his phone to show me something, and scrolled past an album with photos of just her, which I pretended not to notice and wasn't overly bothered by since we all have old stuff on our phones. Until one day when we were visiting his best friend whose wife also used to know X2, my bf and this friend's wife got into a long conversation about the awful things X2 did to her and how terrible and manipulative she was. I stayed out of it, and actually left the room to do my own thing while they talked so I didn't have to listen because, for the first time, I was very bothered by the topic. Later that night, my BF and I ended up talking about X2 and the comment he made on our first date which now haunted me. I wanted to know what attracted him to such a terrible person in the first place and he assured me it was only lust and that he used to be "obsessed with her". I wanted to know why he kept an album specifically of her, when him and I dated for much longer and he never took photos of me (typical jealously, i.e. "where's my album?"). He said he didn't ever look at them and was just lazy about deleting them. He also has had quite a few girlfriends before and after her, but she seemed to hold a special place in his heart (phone). He then voluntarily opened his phone in front of me and deleted each photo of her. There were many... from photos of her dolled up on their dates, sitting beside him in a bar, or her in a thong bikini at the beach... to even just shots of her standing in his living room, or cleaning her car windows at the gas station. I saw how gorgeous this woman was, and clearly how into her my SO must have been to have taken so many random photos, while he has never shown interest in photographing me when I'm dressed up, down or otherwise. ------ It took a long time after this, more conversations and my SO's reassurances, before I finally got past the urge to compare myself with this woman. He did make an effort after to take photos of me when we were on dates. That effort has since tapered off, but he tells me regularly how much he loves me and compliments me (and I do the same), and he often brings up marriage and kids and buying a house together. I feel we are in a good place and have positive feelings about a future with him. In spite of this, there have still been a couple hiccups in bettering my self-esteem, now related to the model ex-GF I first mentioned (lets call her "X1"). During the summer he asked me Google something on his phone while he was driving, and his previous page immediately opened, which was her Facebook profile and a beautiful photo of her. He saw that I saw it, but I didn't comment and just searched what he asked me to. Rationally, I know everyone checks up on their exes from time to time out of curiosity and it means nothing, but I was bothered by it. So that night I had to know what X1 had that I didn't, so much so that his friend from work felt the need to blatantly compare me to her and hassle him for not pursuing her instead. My BF explained that when they were dating, she went to visit her family in Venezuela and came back with breast implants, which is why he broke up with her. He also said she was crazy, talking to her was like talking to a child (she was 20 and he 26 when they dated), and that in comparison I am natural and real and that's what attracts him. Talking it out with him helped me feel much better about myself and resist the urge to unfairly compare myself with something I will never be, and our relationship has continued to stay strong. ------ However, last week he again asked me to look up something on his phone, and when I went to a new tab in Google to search, one of those shortcut thumbnails that are in the new tab screen was that of X1's Instagram profile. Again I just ignored it and searched what he asked for, but for the rest of the week it sat in the back of my mind and ate away at me. So I did what I hadn't done since I was a 20-year-old in a dead-end relationship (and thought I had outgrown), and I snooped his Internet history searching her name. I found that he's been looking at her social media profiles and photos extensively about twice a week, for as far back as his Internet history goes (about half a year). I clicked on some of the links and they were photos of her in clubwear and "bralettes", beauty shots, as well as casual photos and short videos. He has even been looking at her photos and videos posted in her boyfriend's and friends' profiles. He doesn't have a profile himself, so it's not like they show up in a feed prompting him to look. I checked if he searched other people's profiles regularly as well but it seems to be just her page that he keeps returning to. What adds insult to injury is that I actually dress similar around the apartment, yet my BF has never snapped a photo of me dressed like that so he could look at me later when we're not together. And if X1 is so crazy and fake as he claimed, and if he broke up with her BECAUSE of what she did with her body, why would he be checking on her so frequently with what seems like an obsessive level of attraction? Him knowing how uncomfortable I am about being compared with this woman, and still regularly checking her out like this is really hurting me and I don't know how to confront him, because we have already talked about it so much and I know I can't force him to stop looking. If it was just once in a while I could understand, but twice a week for months means this woman is on his mind regularly. I love my SO and what we have together, but I hate these feelings of insecurity I am having from things I cannot unhear or unsee which are affecting my happiness. ------ TL;DR - I was compared to my BF's model ex-GF by his friend and my BF knows how insecure it made me. He spoke about her very negatively and seemed to not be attracted to who she is, but I found out he has been looking her up on social media about twice a week for at least half a year. Aside from this and one other hiccup (a similar ex-GF issue that has been resolved), we have a strong relationship and talk about the future like marriage and kids. I love him immensely but my insecurities about this ex-GF's prevalence in my BF's mind are making me very unhappy. Would like some perspective.