I'm lost and confused

I'm at a loss as to what's going on and I don't know what to do or how to proceed. There's this guy at work who I had never really spoken to because we worked in different departments and he was always just very serious with me even on the few occasions we did cross paths. It's like he had an aversion to me because he treated me so differently than any of my other coworkers. However, my tasks at work changed and I found myself needing to interact with him for work and what started off as texting solely for work related reasons escalated into a bit of just light teasing and then somehow we started flirting which was such a 180 compared to how he used to behave around me. It's all fine and good, except for the fact that he's married and I know it because I've heard other coworkers mention it right in front of me and him in the past before we started talking to each other. I know I don't want to be a fling for him and I told him so, and I'm not deluded into thinking that anything good could come out of this. Honestly, knowing that he's married makes me feel guilty regardless of the fact that we haven't done anything physical, but I do wonder if our text messages cross the line... he's flirty, calls me beautiful, comments on my physique, says things with double meaning, innuendos, etc. In passing he mentioned that we had a thing going on but really, what would you call something like this? We don't really talk much about our personal lives and I hardly know anything about him except his age, that he's married and has kids (from my coworkers). We flirt, have some banter, talk a bit about work, etc. I find myself looking forward to his messages more and more. I find myself wondering how he'll respond or how the conversation will change over the course of the day. I feel like a giddy teenager all over again. However, on the days we don't talk I find myself at first being a little disappointed, but then the calm settles in and I'm okay with not talking to him and I struggle to see why I was looking forward to hearing from him. During those days I find my resolve and find myself wanting to stay away from him, but I don't know if I want to stay away from him because I don't really like him or because I know it means trouble. It's been a while since I've been in a relationship simply because I've been caught up in other things and didn't want to date and honestly I find myself struggling with all of this in part because I don't know if I really like him or if I'm attracted to him solely because it's been a while since I've dated. I'm still not really ready for a relationship because there are other things I want to focus on, so I wonder if part of my attraction to him is because I know I can't have him and that makes him safe in a sense? Truth be told, he's not my type and we don't share interests. He's the kind of guy that I wouldn't bat an eye at or even give a second glance if I was just out and about. Also, he's a few years younger than me and I've never been attracted to younger guys... and yet, here we are... and I wonder if maybe I am attracted to him because usually younger guys are a turn off and so is the fact that he's not typically who I'd be attracted to and I do find him attractive against those odds. The fact that he's married is always in the forefront of my mind when we talk and I find myself wondering why he would be doing this if he's young (we're both in our 20s) and definitely can't have been married for more than a few years, which raises a lot of questions and just makes him seem like he's not a good husband and yet... he still makes me smile and I find myself happier when I talk to him. Have we crossed a line? Is this considered cheating? Do I like him? I really wish I knew because right now you could ask me and I'd say no, it's just harmless flirting, but then he pulls me back in and really, I couldn't say no and mean it.

Yeah, that's what I was thinking too. I thought maybe he liked the validation of being flirty with someone other than his wife. I know it's not good for me, but again, I kind of liked it because it gave me an outlet to also be flirty with someone without it leading anywhere... But then again, I do feel guilty because he has a wife. Without my prompting his messages in the past few days have extended past just being while we are at work and he now sends me messages after work when he's clearly at home with his wife. There have been a couple times in which he'll text me and if I don't respond he'll later send me another message and now I'm struggling to come to grips with that but I do feel less pressure to respond and I feel myself not as attracted as I thought I was.