i slept with his friend before i knew him, we really like eachother but he said he cant like me back.

So about three weeks ago I went to a club with my seniors of my junior year. So this one guy lets call him David, now me and david ended having sex that night but I have regreted it ever since, but a week later we went to a student weekend and partied there, so I met one of his friends lets call him, Mark, that was aswell in te same school, long storie short its 4 in the morning mark and I do not know how we are getting home, and let me tell you we where about a hours drive from home, we get a lift with strangers and i had to sit on his lap in the car, We ended up making out, I was lovestruck. But he told me he was still a virgin which doesnt bother me. We talked for the hole week and then we decided to go clubing last night, he was quite and distant, but while we where alone in the car before he was sweet, caring, loving, funny. But with his friends he was so weird, AND DAVID WAS THERE. I was really drunk so i told him i liked him, because i do. He said he cant and that "its a guy thing". So wtf because i like this boy. Maybe its me, I donno, he just became weird. Help me.