How can I stop liking him?

There's this guy, and we have chemistry. I really like him and I get all glassy eyed and feel sorta high when he's around. It's embarrassing because I'm normally pretty poised. I don't know if he feels the same but I have noticed he's been avoiding me a bit, as of recent. Problem is, he has a girlfriend and I have a boyfriend, and we've been with them for a while. So, how can I stop having this reaction around him? I can't avoid him altogether because we have classes together.