Should I end the friendship?

Lindi

This is my first semester of college, and I met a guy in class. We have all of our classes except one together so we are around each other a lot and consequently have become pretty close. I feel like we really click and I can be myself around him and he has said many times that he agrees. We talk 24/7 even when we aren't in class. The problem is that he has a girlfriend and I feel like our friendship is becoming borderline more than just friends, even though nothing has ever happened between us. I would NEVER cheat or be the girl on the other end of the cheating, so this situation makes me a little uneasy. He has mentioned a few times that he doesn't think he will be with his girlfriend much longer but I still feel a little guilty about our friendship even though nothing has happened (or even been suggested). I don't want to lose him as a friend but I don't want to cross any boundary lines either. What should I do?