I have boy trouble. I want to ask out my friend, but I am not sure he is going to say yes. Plus, he said he had a girlfriend when we talked during school. Plus, my parents don't want me to date.
Sounds like you've been giving this guy a lot of thought. The volleyball game in your head — back and forth: yes, ask him: no, don't ask him; maybe so, what if he does say yes? — is the trouble you're having, rather than with the "boy" himself.
While you wonder about this young man's availability as more than a friend, your parents are saying that the time is not quite right for you to start dating anyone. Friendship is a great foundation for any relationship, so it seems you're building on solid ground.
Understand that your parents can set rules in your best interest. If their rule is "no dating until you're 16," you may have a year or two to go before you can either ask your friend out or accept his invitation for a date. In the meantime, you can get to know your friend better by hanging out with him in a group or sharing classes or extracurricular interests. You'll probably discover all sorts of new insights into this person, including whether he's currently committed to someone else. (Of course, that attachment could change, and you'd be likely to find that out, too.)
Importantly, keep the conversation going with your parents. They were your age once, so they really do have a clue as to what you're going through as you bounce around different emotions.