I need serious advice BEST ANSWER GETS 10 PTS !?

[lola]

I have cut off communications for good with my ex about three weeks ago, but we have not been together for a month. Im 17, and he's 18. We were together for almost three years (next month will be three years).
So i found out that he has been kissing this girl, messing around with her, and he lied about it. I have always had problems with him, but this is what made me cut him off. So about a week ago, he has has been talking bad about me on twitter and facebook, and i never responded to it, but recently he has stop, but the girl he was messing around is just stupid to me. I mean it's clear as day that he is most likely using her to get me off his mind, because he use to couldnt stand this girl. Now he post things about how he really likes her, and little stuff like that. It's bs to me (well i try to think like that), and i pretend it doesnt bother me, but some days it does. I KNOW that im done with him, but it's hard, even though i talk to my guy friends more, it's still hard, because he hurted me. I know im young and a lot of you think im stupid, but i dont care, i feel like our whole relationship was fake, and i moved on by talking to other guys, but my ex has caused me to have major trust issues.
I mean i thought i loved, well i did, but i feel like it's fake. Like i hate him so much, and im so bitter about it, i wish something bad will happen to him.
Those two are probably going to fall apart in a matter of time.
I just need any advice you can give me

[Sir]

Get over it is pretty much all you can do it's never easy ending a 3 year relationship you're going to feel how you feel. The girl he's talking to that he used to not like but now does may just be a way to get you jealous.If he's talking bad about you on FB/Twitter it's more then likely a way to get you to talk to him if you really have stopped talking to him.

Also the best thing for you to do is just ignore it i mean ex's usually get mad and retaliate with words or actions but they have to stop eventually. This girl i use to see still talks mad shit on me for no reason just to make herself look good.