Why Are Some People So Very ?

I have a friend who isn't physically gay like...loves men gay, He just acts really gay. I mean we're friends and all that but he seems to flicker on and off whether he's in the mood to be friends at that particular moment. Today we had double D.T and he was absolutely FINE at the beginning of period 1 but as I started talking to his friends more he got really quiet and upset, even thought I wasn't ignoring him at all he just started to ignore me. I thought at the time it could be jealousy as there was a kind of thing going on between us once...but now that's over but I still like him. He told me last week he was generally flirting with me in P.E and that braces wouldn't affect me and I didn't know what to do as I didn't know if he still liked me or not. It's just really annoying all of this and I don't know what to do!