This boy asked me out, I really don't want to bring him down and make him feel like crap, what do I say?

Right on girl. I'm the same age as you and have been in the exact same situation. I just told the guy pretty much what you said. If he really likes you, then he'll understand and should respect that you want to focus on God right now. I know that if you just tell him the truth it'll all work out the way God wants it to. Good luck!