I'm a 14 yr old boy and, to be honest, I don't know why I'm on this site, but you shouldn't hide how you feel. Flirting can mean a lot, as I can not, at all, stop myself from flirting when talking to girls, but that doesn't mean I don't like them either, although you did say you know he does like him. Tell him how you feel and I'm sure you're thinking 'Easier said than done.' and, yes, it is. It will cause an awkward moment and will be much worse for you than him, but then he'll have to respond someway, because it's impossible not to do anything. Mystery is the worst part of any relationship. He HAS to know how you feel or he is going to be in the same situation as you. Tell him you're not sure, but you want to try anyway, because you do like him. Go for it!