please anyone give me advice!!

okay me and this guy I like flirt a lot...We were at this party and I told him I like him he said he thought so but wasn't sure. The problem is that he has a girlfriend! They have been going out for a while too!! but we flirt and stuff and I think he likes me too!! but he hardly talks to me at school anymore. Whenever I see him and his g/f I get really depressed! I don't know what to do! Should I call him and talk to him about it (I have never called him b4) or should I talk to him at school but I guess that would be kind of hard. Please just tell me what you think I should do! I really like this guy!!

PLEASE PEOPLE GIVE YOUR OPINION!!

I guess maybe you are right...but still I know he likes me because he told me and he flirts all the time! But I would be mad if I was the girlfriend and someone was flirting with my guy but still I really love him! And well I think I might call him and talk some stuff out with him....maybe if I get up enough nerve to do it. thanx for your advice!
Love always & 4eva »-(`v´)-» Chelsea