Prom Problems

Ok so I have a problem. I think I want to go to prom with a guy but don't know if he wants to go with me. I want to ask him to go with me but what if he is going with someone already or he doesn't wanna go with me at all? I am scared to talk to him because I am afraid it might slip and then he will reject me right then and there. Geesh now I know what it must be for the guy when they ask girls out. Totally nerve racking. I just wanna know if he wants to go with me. Because he is the only guy I wanna go with. I feel myself when I'm around him so I think if I was to promote my going, it might as well be with someone I can be natural around.