Even if he says no, it might be worth it to get it off your chest.
It depends on what you want to happen. Do you expect him to return the same affection, or do you just want to let him know how much he means to you? That said, he probably already knows how you feel. Also, at your age, your feelings my be somewhat confusing for you. We gay guys are very "safe" for straight woman that are insecure with their own sexuality. They can act like they are coming on to a man, without the fear of being rejected, because you already know he is not into chicks.
if u want u can or u can turn him into a girl :D some my gay friends like to be turn into girls its fun dressing them up :D
Nope. If he's gay, it's only gonna end in hurt for you.