Trying to me make me jelous or trying to play me?

there is this really cute guy, he was really trying to get to know me and all but i was just ignoring him in the begining. But when i finally wanted to ask him out i found out that he started to go out with another girl (a girl that he has no interest in at all). But wile he was going out with her he still stares at me alot everywhere!! in the subways, in the hallway and now i here complaining a lot abut her. what does all that mean?? Does he still have feelings for me. Did he try to 4get bout me but couldn't. try to subtitute me 4 that other girl?