Relationship over after 5 1/2 years...

I'm not here for pity or anything like that, I just need to get this off my chest.

When I was 16 I met the most amazing guy. He was the best. He treated me like a queen. Fast forward, in December 2015, right before our 3 year anniversary I found out he cheated on me. The girl told me and even though he denied it all, I still believed her because I figured she had nothing to lie about. I still stayed with him. Fast forward to June 2016, I found out he cheated on me again. This time I left. We went separate ways but by the time summer was over we were back together. He promised he would never ever do it again. He was focusing on working on himself and being a better man. Again in April 2017, the worst happened (not going to disclose), and I left him. But once again we got back together by August. We couldn't live without each other. He begged me to work on things, he promised to make things right and work to be better together. I could tell things were getting better, we even tried having a baby but for the past 8 months, it never worked. Now that I sit here, I'm kinda glad it didn't because there is not telling where I would be if it did. He wanted a baby, he always talked about it. I went on vacation at the end of February for 2 weeks and we didn't talk much because he's been going through stuff but when I got back, it all went back to normal. I felt more in love than I have been in months. We both live at home so we got a hotel room and spent the night with each other. We spent that day together, the next 2, and he was sick Saturday-Monday. So Tuesday before I dropped him off at his friends house I told him I felt iffy. He said why? There's nothing for you to feel iffy about, I would never do anything like that again to you. (He knew what I meant). So the next day after I got off work I was on IG and randomly clicked on a girls page and there he was..... Pictures of them kissing, hugging each other, with the girls brother and mom. I felt so devastated, I was so angry. I called him because I couldn't figure out where he was. And once I asked him, he hung up... So I commented on the pictures to let them both know I found them and I kept calling him.. he texted me and said "I'm done stop calling me" then he blocked me on Facebook and IG and made her block me as well. I knew then and there he took her side... After 5 1/2 years he took the side of someone he barely knows over me, someone who has been there for him through everything he's been through. I never judged him, I was always by his side, defending him. He hasn't reached out to me since and now I'm scared I could be pregnant. Although we've tried several times and never succeed, it'd be my luck that this time it does... I just don't understand how he could do this to me. He pleaded to me that I was all he wanted, he wanted us to work terribly bad, he's been trying to get me pregnant, he wanted to move out soon together, he always told me how much he loved me.. I'm just so confused and angry. I feel so numb. ☹️ I blame myself because I should've just left him the first time. He was my first love, I could never see myself not being with him..

This is just so hard..

Update: I forgot to mention I'm going to the doctor this week to take tests since he did cheat on me. So I'll update after that. And I just found out the girl isn't even out of high school yet. He's two years older than me so that makes me sick 🤢