My ex boyfriend

Okay so I broke up with my boyfriend in February and after that we were both confused w our feelings and what we should do. For a long time he was asking for me back but then all of a sudden I see him with another girl who he apparently has a thing with. I reacted even though I shouldn’t have it bothered me so much and I don’t know why. He got really mad with me for being annoyed about it but I know he still likes me. I feel like I miss him but I’ve ruined everything Idk what I should do.