It's a bit baffling, but I've learned to really abide by the saying "sh*t happens." Guys, and even girls, have their reasons for unexplainable behavior that just doesn't make any sense, no matter the situation.
Don't let the sweet talk get to you either...if he finds you attractive, of course he'll say that–but so will many other guys who feel the same. Just because he said it, doesn't always mean he has deep rooted feelings for you; and just for that reason, it's easy to turn it on and off.
After reading your recent comment, he was probably afraid of commitment. You'd think it's simple right? If a guy likes a gal, then why doesn't he just stick with her? Well there are many reasons. First of all, you both are probably very young. While you're prepared to settle into an exclusive relationship, he's probably just getting ready to play the field. Maybe it's not him, but rather his friends and the pressure that he's feeling. Like Malleboyz said, there are just toooo many reasons to have to analyze. It's not worth it babe!
I would say just try and get past it. There is no point in analyzing this situation. If you try and spill him for answers, it will get you nowhere, and also, you'll be backing up his reasons for not calling you in the first place.
It is actually the best thing you can do. Move on. Get sexier. Get a new hairdo and buy a REALLY sexy outfit. Go out and meet someone new. Love your new self.
The funny thing is that once you move on, and he notices, he'll probably come crawling back...cause all boys want what other boys want.