What can I do to get over this guy?

I think you have to take time to think like you are doing now, find something else besides a guy to occupy your time and then once you are okay with you then go find a guy that is all yours. You were very jealous of a man you could not have. When you went and told his girlfriend that wasn't for her that was for you in hopes to win him over that's really not cool. Also just because you think you guys were meant to be together doesn't mean he sees it that way. People will do what you allow them to and that is exactly what the guy did... next just make sure you are getting out of it what you want or need and you should have no issues letting him go. But don't go after a man who is taken that should have been immediate flag to move on.