My boyfriend cheated in the past, i'm finding it hard to forget and move on and.?

should I be worried that quite a lot of girls post on my boyfriends facebook saying ''hey ;)'' with winky faces.. he cheated on me in the past and I am finding it very hard to trust him again and I am constantly worrying about where he is or who he is texting, I look at his facebook and twitter page 24/7.. help :( i'm 15. I know i'm young still but I hate being single, I can't break up with him

break up with him before you get really hurt sweet heart. you sound like me you fall in love very hard. good luck