I think he said "I love you" How do I find out w/out actually asking him?

Recreate the circumstances that made him say it before.

Or, do as Kimberlyinspired said, just do the casual, "luv ya" thing. He might be worried that you haven't reciprocated his feelings.

You could just ask him, "Did you say anything to me in bed last night? "

Just say I love you to him. Or make it casual. When you both are to part ways, say "luv you" and he may say it back too.