Hung up on my ex

I was best friends with my bf before he was my bf, then we dated for three months. He meant the world to me and still does. I found out he was cheating and I got really hurt. I left him. The break up was pretty nasty because we both said some pretty mean things. That was about a month and a half ago. He has had three new girl friends in this time. I'm still not over him though. We're only 14 and I knew it wasn't going to last long. But for some reason I fell in love with him, and not your middle school "I love you" stuff. We went on dates,(are parents had to drive us😂🤦‍♀️) we called all the time, we talked about everything, we went to family stuff, and we had sex. That's a different topic but we did. I'm just so hurt that he would "hit and dip" but then again did he really? Idk I just need help getting over him and I don't know how.