Ruined the best relationship... not sure of next step

Just had to clarify that in the title Warning: this is going to be long and maybe a little bit rambly. First to elaborate, here are the three important people in my story, fake names of course just in case Me: Kay, 21F Luke:22M-ex boyfriend/best thing that ever happened to me Jack:22M-childhood best friend to Luke, few year best friend to me Here’s where everything starts. Luke and Jack are both from the west coast. I am from the east. In late 2015, Jack moved to my area for some pre-college work. He had no family and hardly knew anyone. He went to church with an older lady that lived in my apartment building. We met through her. In early 2016 Jack and I become basically instant best friends. He’s funny and kind. My family treats him as their own. A few months later, I develop a crush on Jack. I jokingly admit it to him knowing nothing will come of it. He says he has similar feelings but we both know it would never work out for multiple reasons. We jokingly agree that if we’re single in ten years we’ll get married. My family gets in on the joke but super encourage it too, since they really love Jack. Nothing too serious and nothing romantic ever happens. In the summer of 2016 I moved out west for college. My campus is about 6 hours from J&L’s hometown and coincidentally the same school Luke and a few of their other close friends are attending. Jack jokes that I should hunt them down so when he attends the next semester we can all hang out. It never happens, and Jack and I talk much less for the next few months. Fast forward to January 2017. Jack moves to the campus to start school. We meet up one time in the first month and he doesn’t mention his friends at all. A couple weeks later he shows up to the diner my roommate and I are having lunch at with a group of guys adamant on introducing me to my ‘new best friends and eligible bachelors’ because he’s a goof. All I remember thinking or hearing after that is anything Luke said. I kept thinking ‘wow this is the most attractive guy I’ve ever seen’. That meeting was all it took for my roommate and I to become part of their group. All of my free time for the next month or so was spent with these guys getting to know each other and having the best time of my life pretty much ever. Luke was my favorite, and I was never sure if it was because we had a lot in common, because he was the nicest person ever, or just because I was attracted to him. Maybe all the above. He became my go-to person for anything and everything. He deserved the ‘best friend’ title more than anyone I had ever befriended before. About mid-March I had accepted my fate that I was pretty much falling in love with him. I wasn’t going to tell him though, despite how my roommates wanted me to because ‘he’s so in love with you!’ On April Fools Day of all days I got super drunk and told Jack how I felt about Luke. I don’t remember it too much but I know it happened, because he knew that Luke really did feel the same and let him know all about it. I didn’t know this until almost a week later when Luke said ‘so when are we going to go on our first date?’ I played dumb until he explained it all. From then we went on our first date, and our second and third and so on until it’s December 2018, we’ve been dating for around 20 months. We’re the happiest couple I had ever met. Not perfect obviously but everything is going great. We’re at my house for the holidays and he’s joking with my sisters about marrying me. We had been talking about it a lot lately and I was semi-expecting a proposal at any time. One of my sisters brings up Jack and I’s deal and ‘relationship’ which freaks Luke out. Apparently in the past two years, neither Jack or I had mentioned any of that to him. When we were alone that night he brought it up to me and he was very upset. He thought that Jack and I had a previous relationship we had hid. That spurred into him thinking that all the time we spent together after our relationship started was me cheating on him. I couldn’t calm him down the rest of our trip. Nothing I or Jack said could convince him otherwise. After two weeks of silence and then more fighting and then more silence he broke up with me. I had never felt heartbreak like that. It was the worst few weeks of my life right after. I had shut out all of my friends. I finally started answering texts and phone calls again. I met with Jack for lunch and found out that he hadn’t even been able to talk to Luke since then either. He was almost as devastated as me. I felt terrible, because I had never assumed he would cut out his life long friend and tbh I didn’t even think guys had fights like that. I was a little naive. We comforted each other for a while after that. A little too much I suppose. Because within a week of that Jack was over at my place every night. We were having sex to make each other feel better but never mentioned it to any of our friends. We were each other’s secrets I guess. Move along about another month, and Luke is back in both of our lives as friends. He had apologized to me for overreacting but explained that he wasn’t sure we could ever be more than friends again for his ‘personal reasons’. Fast forward again. Now it’s March 2019. I have my friends, my classes, and my full time job. Life’s going pretty okay. I miss having Luke around as anything more than a friend. I love him more than anything. Then out of nowhere it seems, I find out that I’m pregnant. I know that there’s no chance it’s anyone’s but Jack’s. I’ve always wanted kids and I don’t doubt my ability to raise a child on my own. What freaked me out was the situation in which everything happened and how to even tell anyone. Now it’s May. Jack has a new girlfriend. She’s lovely. Two weeks ago before I started really showing, Luke mentioned maybe starting things again slowly. We’ve been trying that and it’s been wonderful. That’s going out the window, because now I’m showing and my friends know I’m pregnant. My family already knew but think they don’t know the father. Everyone’s questioning me and I keep saying that I need time, which they accept but won’t forever. Neither Luke or Jack have mentioned anything about it to me and I’m not sure that they have even noticed or heard yet. I don’t know how to tell Luke that I’m pregnant at all, let alone with Jack. I know he’ll assume he was right all along. And probably be mad about me hiding the pregnancy which it very fair. Jack is happy with his girlfriend and I don’t want to ruin that. I don’t know how to tell him either. And I don’t know if I should do it before or after talking to Luke. How do I tell them? Who do I tell first? I am so lost and have no idea what to do. I’m already scared to have this baby on my own. I know I’m capable but still terrified. And with all this on top of it I can’t stop freaking out every time I want to tell someone. Please someone offer me a little advice. TLDR: Had a joke with my friend of three years that we’d get married someday if we didn’t meet someone else. Met his lifelong friend and dated for 20 months before he heard of the joke from my sister. Ended relationship with me despite nothing romantic ever happening and accused me of cheating with friend. Seeked friend for comfort and had sex, becoming pregnant. Ex wants to start relationship again without knowing about baby. Not sure how to tell either one about pregnancy and I’m out of time to hide it.