Well you got yourself in a doosie, didn't you. Sorry to say these situations never work out to well.
The best advice I have is to swallow your heart and maybe have a easy going conversation with him about taking it to far.
Say something like, I think we should stop sleeping together and say your concered about the friendship, stress that the friendship is important and that you don't want either of you too get hurt.
Then see what he says? Use your gut to measure his reaction, facial expression, body language, etc. If he says your right, most likely he is just enjoying the sex.
If he pushes that he cares about you, then say, well can you see us together some day, or is this just for fun?
Say I need to know for myself, and for our friendship?
That should give you enough to go on for now.