yeah, same here. Just fill your life up with lots and lots of activities, work, school, club, martial arts, sports, shopping, chores, going out with friends etc etc. once you get busy, there won't be a second left to think about him.
I don't talk to my ex-bf or think anything fond of him. I've just trained myself to think like we never met because yeah, he's been with many many different girls since me, he's not worth my time, thinking of him takes up my time, think of him and moping about him and what went wrong is needless worry because the bastard doesn't even think about me anymore. So I think about it like this, my life is more important than his and I should focus on myself.
So take care of yourself better, take time out for yourself and do the things you love to do to make you happy and forget to needlessly worry about what this guy is doing. chances are he's not even thinking about you if he's with another girl. That's how I stopped thinking about my ex. good question ^_^