Help?!!?

I'm not happy with myself. I've been studying (well, that part I like) and although it's been 3 months since I came back from that stupid place I still can't get over my ex. That's the part that I don't like. It feels it has been so many more months and that's getting harder and harder and now i'm starting to belive that I need therapy. Maybe it's PMS, or maybe it has reached a point where I can no longer control and deal with all of this.
I'm so upset, so sad, feeling so depressed and I just don't wanna feel this way anymore and I just don't know whatelse to do! It's such an overwhelming feeling!!!! I don't talk to the guy, I have no idea wht's been going on with his life, don't run into any of his friends and yet, his on my mind all the time.
It got to a point when I'm trying to fall asleep and all of my thoughts lead to him, even if I'm thinking about another guy or a quiet place; in some messed up way he pops up in my head; it's pathetic, ridiculous and I'm completely aware of all, still...
I just wanna let this go, it makes no sense to be in love with somebody that doesn't love me back I wanna forget and just be hsppy either alone or other person.
BAH! I hate this!