What if he's only with her because he doesn't know I want to be with him?

So there's this guy. His name is A.j. My freshman year of highschool (I'm going to be a junior this year) I was dating this guy named Max for about a year but when I met A.j. I couldn't help but want to be with him so I dumped Max for him. But I was still very conflicted about Max so I went back to him and it was awful. But miraculously A.j. and I remained friends through that. His friends say they've never seen him so down after I did that. But now, we've been 'just friends' for awhile. That means we had a few cles together and would talk occasionally but it was awkard for awhile. This summer, we're basically in the same group of friends now, we've gotten close again. Like, we text non-stop until like 4 in the morning. We talk about everything, what we want to do with our lives, where we want to go, what we want to be. He is literally me in the guy form and we've both expressed this to each other many times over. The problem is, in our gorup of friends, it's all guys and they've accepted me as an 'honorary bro' haha. I really want it to be more than that with A.j. and I. We can talk endlessly about anything. I go over to his house and have dinner with his mom who loves me. We play hide and seek and listen to old cds. Last time I was over, we ended up on the coach together me laying on his shoulder and just the way he stares into my eyes I'm so sure we were going to kiss. But then I had to leave. He's always so protective of me, whenever something even minimal is wrong he tries to fix it. I might legitimately be in love with him, but if not that I really really like him. Here's the kicker: he has a girlfriend that he acquired during the 'we're just friends' phase. But I feel like things are changing. He chooses me over her anyday and makes it known he doesn't think it's going to last (hint maybe?) and he asks very interested a lot of how my love life is. It's not as if he's some trying to have both of us. We tell everyone were best friends and that's it. I feel like we both want more, but we're both afraid but I could just be imagining everything. Also yesterday he askde if I was busy and was really dissapointed when I told him i already had plans, I feel like that meant something. So tell me what you think. If you think he likes me too, what should I do, tell him now and break up his relationship like a tramp? Wait until it's over? Wait until he tells me? Thank you so much.