If this is for real, then why do you say you are 17 in one sentence and 18 in the next. It does make a difference. If you are 18, go flirt with him and ask him out. If you're 17, wait until you're 18 and then go flirt with him and ask you out.
The reason why I asked if this is for real is because I swear I read the exact same plea for help about a year ago on another dance bulletin board. Well, maybe this kind of situation is just more common than I ever imagined, and that's why it keeps popping up!