Ex boyfriend? 😫

My ex boyfriend who I loved, still do. We dated well over a year ago, going on to be the 2nd year. Anyway, he's got a girlfriend again and my heart keeps breaking when I see them around. I just started to feel better about him and realising I don't want him. But he started talking to me non stop for 2 weeks. A few weeks ago. And he was telling me that he still loves me and stuff and we talked about everything and stuff about our relationship and breakup. And just like that, the feelings came rushing back, now he's dating this girl that I've never gotten along with, and she hates me. And I just feel the breakup pain, over and over again. She told him not to talk to me, so he stopped. Which I guess I understand, but she is a slapper, she goes around having sex with a ton of guys, one relationship after another, one guy after another. She's only 15. I really miss him and I hate seeing him with her. She sees me at school and latches on to him, she does it on purpose. What do I do? :(