well it's because he has you now. Men like the thrill of the chase and they want what they can't have so you need to stop making yourself so available to this guy. Maybe you come across as clingy to him? Either way, I would stop contacting him until he gets back to you. Don't respond right away either, you don't want him to know that you're waiting for him to call/text/whatever. If this guy has any interest in you at all he will contact you, but on his time.
I must also add that it sounds like you're more into him than he is into you. Been there before and it fucking stings like a bitch. The best thing you can do right now is find other things to get involved with. distract yourself from this guy and see just how far he goes to pursue you. Men like the chase, so give him something to chase after.
If this guy says you're not officially boyfriend and girlfriend, and if he never responds to your texts...sounds a little far from 'absolutely perfect' to me.
If it were me, that would be enough for me to lose interest in a dude--no matter how 'perfect' they seemed. That's just me though--but if you want to make this relationship work, it sounds like something you need to talk to him about. The longer you put it off, the harder it will be to get it out in the open, and the more it will hurt if it turns out he just wants to date casually.
My friends say that I tend to be either extremely vague or painfully blunt. In your case, I would just go ahead with being painfully blunt, because I don't see how beating around the bush will get anywhere. If you ask him straight out about it, then you'll get a straight answer. If it's not what you wanted....well, the world won't end. It'll be all right. ^.^