It is possible that a guy with girlfriend likes me?

There is this guy I know that has a girlfriend. I noticed that he is always watching me, look me in the eyes a lot, and stuff like that.
Today he said something about her, and looked at me quickly when he did that. I know its difficult to answer this one, but he was trying to make me jealous? How should i act around him?
Thanks :)

Even though we are in relationship doesn't take away the fact we look at and lust for other women.

Stop worrying about a guy who's already taken

Good choice of sceen name, OP ~ Well done!