What do i do if my ex boyfriend is making my life terrible?

Well i broke up with my ex for someone i really liked but after that he begged to have me back so i went back with him.Then he broke up with me for this other girl after that i was happy back with this guy i really liked but my ex called me and kept bugging me till i finely said yes he broke up with me and now that guy i really like want talk text or text me he want even say hey to me when i walk past him. At my ex just was acting like a jerk but then he called me and acted like he was this person named petter. I thought petter was a good guy and i told him how much i hated my ex and what i heard about his girlfriend and trust it was not good stuff. Well i wasn't mad enough he went and told everybody about what happened. After that he acted like he acted really perverted with everybody he seen when his girlfriend wasn't around even me. I stared to wonder if same thing to me and really started to who he really was. Just a couple of days he told his girlfriend that i wrote him a two page love letter about how much i still loved him. Which was a lie i don't for him at all anymore. Now all her friends hate me most were pretty good friends with me. Before all that he kept telling people that the reason why he broke up with me was because i was ugly. In that same day when we were walking out of cl he came behind me and said hey beautiful. I don't think i look that bad anyway i have had a lot of people to say that I was hot. Yesterday he kept feeling on me. I almost forgot to tell you im kind of young bellow 10th. He didn't really wasn't to bad until after i rejected him that's when he started treating me like crap.