Hello, Stayed the night with my boyfriend last night, the bed was shaking so I looked over my shoulder. He was scratching his butt, like.....between the cheeks. Then he smelled his fingers. When he realized I was turned toward him he started fake snoring. How do I address this situation without making it awkward?

Too late for awkward! That ship has sailed. If it grosses you out, tell him. Maybe he will stop doing this in your presence.