How long to get over a break-up?

I was with this popular guy for a few months...everyone in town knows him or has slept with him...real (found out too late about that LOL). Anyway, I see him on facebook and I don't have any friends in person, most of my friends are on facebook, and they invite me to do things, but I'm a homebody and don't go out often. I just get so irritated that guy used me and took advantage of me, and he has all these friends that like him. I'm pretty sure he's telling people I'm a b**ch. The thing is, when I do go out I'm going to be seeing him there's no getting around it. How can I just realize I'm better off without him? He's really out of shape and fat, I don't see how he gets guys at all. I'm in really good shape, and I fell for his nonsense. I suppose looking good is the best revenge. He's about 30 pounds overweight, and I'm thin and pale. I don't see how he could get in shape by the time I put on a few pounds and get a tan. What do you think? How can I feel better about this situation? I have two weeks before I plan on going out to the bars. Should I tan and workout like crazy and then just be real casual when I see him. I have never argued or insulted him so I won't start now. What advice do you have on getting over a real jerk-hole?