Then, you should just move on, if his main focus was you.. then he would be dating ONLY you.. so therefore.. let him go, and remember, there are ONE too many guys out there to be concerned about ONLY one. :] good luck.
I think otherwise to. not to be mean but if he likes you like you say he does he wouldnt be spending time with another girl. instead of being with you. you should go and fine someone else and be happy. dont wait around for another guy who is going on dates with another girl
well if he didn't like her wouldn't he just break up with her for u? sorry but I think you thought right. I would just move on.
hope I helped:] funmail me if you need more advice.