First of all, at your age, you should not be posting or reading anything in Mature Topics; it's for adults.
As for your problem, no, don't tell him you're gay. That's a lie. You should just tell him you're very flattered that he likes you, but you don't feel the same, or, you're just not interested in him like that.
You're better off telling him you just like him as a friend rather than lying. That sort of thing has a way of backfiring---say, when a boy comes along whom you do like and gets the word not to bother, because you're "gay".
Not really??? yes or no. What is the question truely about?
Just tell him the truth, better that he respect you; that is if he is a good guy and really cares about you... if he just wants to get in your pants and through a hissy-fit then he's a douche ignore him. I know from experience, the fake lesbian thing was really upsetting when I found out she wasn't.
You shouldn't lie to him that you're gay just because you don't like him, in the future it'll hurt him worst when he found out you were lying, tell him straight forward that you dont want to be with him. In the past 2 weeks, two guys asked me out, but I told them that I don't want to start a relationship right now ( true ) and that they should find someone else. Tell him there's always more fish in the sea. C: