I Need A Lot Of Help

I like this guy and we flirt a lot, we even made out once on my sweet sixteen, my one friend likes him but he does not like her back, i am friends with his girlfriend and i dont want to mess that up , i once heard they were breaking up but i quess not. I really like him and i have feelings for him, when his girlfriend leaves his house we flirt a whole lot what should i do and does he really like me?