Why would a guy always observe a girl?

[little.girl]

There is this guy I know that go to the same gym as me. I noticed that sometimes when I'm talking to someone he's looking at me, even when its the other person talking, for example. he's contantly looking at my face, my body... noticing my gestures and stuff like that. I'm aware that maybe he feels attracted to me, but I just want to know why he do this all the time! I'm not 100% sure because he sends mixed signals, like this time he called a few people to bring snacks, sandwich and stuff to eat and didn't called me! And he has a girlfriend too...
This is why I think that he do that because he's only judging me and doesn't like me, at all... Guys, what do you think of him?
Thanks

[basilandthyme]

it's hard to say. Do you have any qualities which would make someone stare? Like really big piercings or tattoos or weird hair?

[Agnus]

Because he likes you but is afraid of his girlfriend. If he starts hitting on you, most likely he'll get into trouble. And he doesn't want that.