How do I get my ex boyfriend to want me back? helppp!?

Long story short...we met in college last year and we were together all school year. I felt he wasn't completely committing to me (he didn't hookup with anyone else) but just that I would do a lot of things for him he never took me out to dinner or anything because he joined a frat and that became his life. I was not a priority it seemed like. I gave him an ultimatum in April either commit to me or not. He chose not because summer was coming up and we 5-6 hours away from each other. I was heartbroken but he told me we'd be together again and we aren't done forever (asshole). 3 days later hes making out with some other girl. I confront him he says he's trying to get over me. AH. So i'm home for the summer now and find myself crying a lot. He screwed me over. I'm just afraid this ruined my college experience. Everytime I think of school I think of him and him with other girls. So my question is...how do i handle going back to school? I'm in greek life too and I want to know how I act when I see him. What if hes dancing and talking to all these other girls in front of me? I know I shouldn't be with him but I want that revenge not gonna lie. I want him to want me back. And i'm not trying to be stuck up but he had a great girl! And he isn't even that cute! I don't get it! any suggestions? Does jealousy work? How far can I go with that without making it work against me? HELP and please don't be mean :)