he might really be telling the truth. You might be the girl that he wants to have a relationship with. However, it sounds like he wants to mess around with other girls, or do all the flirting/hooking up/having sex with whoever he pleases without having to commit to anybody. Guys are funny like that--they may want to be with you, but not enough to give up every other girl they might have a chance with. So they'd rather skip out on a relationship until they finally feel ready to give up other girls
It seems to me that he likes you, but also wants to mess with other girls (and maybe even see what else is out there) before committing to you. So he is putting you on the back burner, and he expects you to stay there until he's done with all the other girls, and then he'll go back to you and you guys can do your thing. he wants to have his cake and eat it too.
I had a boyfriend once (i was like 13) and we talked for maybe 4 months. Then a few months later, he started talking to an older girl and they began going out. He told me that he didn't think they'd be together long, and he wanted to be with me when he was done with her (those were pretty much his exact words). So I waited. And we flirted. And I was looking forward to the day that they broke up, so I could be with him again. It never happened. But throughout their entire relationship, he was flirting with me and telling me that when they were done, I'd be next. We even came close to kissing once. He is still with her, I moved away, and that was that lol.
I think that you should stop talking to him. Tell him that if he wants to talk to other girls, then thats fine. Don't get angry or yell at him, be really nonchalant and cool with everything. Then don't call him, don't answer his texts, and if you ever run into him be polite and nice. He seems like a guy who'd lie to you, and you shouldn't really trust him. He's going to keep giving you the run around and its going to be a long cycle that
you have to end. He is a man--he expects you to wait around for him, but you shouldn't. Stop talking to him: it'll probably make him wonder "wow, i wonder what she's doing? who is she talking to now? where is she going?" And if you start seeing signs of him coming back to you again, then I would let him know that if he wants to be with you, then he has to show you that. meaning NOT talking to other girls.
And if he doesn't come back around wondering whats going on with you, then great. It'll give you the time to be with your friends and maybe find a better guy (but don't search for a replacement for this guy)
Good luck