I keep doing this to myself..

I hate how I keep falling for guys that I know I'll never have a chance... I've always had a bit of a crush on one of my really close guy friends, who I guess we'll call B. Well B and I have always been fairly close, we get along well. He's so incredibly smart, handsome and funny guy, he's easily the sweetest guy I've ever met. From the beginning, I told myself that I wouldn't get feelings for him because I knew it would only end in heartbreak. But inevitably, I started getting those butterflies whenever I was around him, he just makes me so happy and it doesn't help that he's essentially perfect.

I came out to him a month ago, of course he said nothing would change between us. I thought maybe I would stand a chance with him, even though I was pretty sure he was straight. A few nights ago at a dance I saw him dancing with/kissing a girl, and even though it was expected to say I was upset was an understatement. I built myself up so much on lies and puffed myself so full of hot air that the fall was even harder than it should have been... That night I cried, and the next day I was sulking around and brooding the whole time, which didn't help that he was by my side the entire time.

I asked B if he had a girlfriend, he said no. I said I saw him with a girl and he blew it off like it was nothing. He made a point of sitting next to me and talking with me even though it was almost unbearable to be near him for me, and I felt so bad because I was essentially ignoring him the entire time and I couldn't just tell him what was wrong because it would make me seem too desperate...

I don't know. I so desperately want him in my life, but I feel like just being his friend is enough and not enough at the same time. Idk if he's bi or straight or even gay, but I can't deny anymore that I have caught the feels. All my friends told me to find out if he likes guys anyway, but I just want to spill my heart to him but for whatever reason I couldn't muster myself to do it. I guess what I'm asking is what you guys would do in my situation.

Tl;dr: I like a boy who seems to like girls, but whenever asked about girls he avoids the topic or flat out denies he has a gf/was with a girl. Idk if he's straight or gay or bi, but he makes me happy and seems to like me. Saw him with a girl a few days ago, asked him about it and he acted like nothing had happened between them. Want to tell him how I feel but don't know if I should... What would you do?