1st: WoW heavy stuff.
2nd: There isn't anything wrong with thinking of a past lover, or what have you, as long as it don't interfere with your normal every day life. Like for example if you stopped showering or stopped eating, then that's a little extreme and I'd say snap the f*** out of it. but if you're just thinking of him then no harm.
3rd: WTF is wrong with you!, you're thinking about a douche bag, d***-less, loser coward that cheated on you, and you even acknowledged his jerky-ness (I had to make up a word to convey my emotions) what dose that say about you?
4th: you know why you can't stop thinking about him, because you think you're not special, that's right, you think you're not worthy of a guy that will treat you like the gem that you are and this need not be, YOU DO DESERVE A GUY THAT WILL TREAT YOU RIGHT, and his out there some where waiting for you to SNAP THE F*** OUT OF IT and find him.
5th: here's a way to stop thinking of some one that doesn't deserve one second of your metal energy F***ING STOP IT ALREADY!
hope I helped :)