I would talk to him how you feel about being his rebound and everything that you're thinking about. He will find it much easier to relate to you and be honest if he knows whats going through your head.
From your post it sounds like you cornered him and lampooned him with barrage of accusations. I'm sure it didn't happen like that but I'm just saying that instead of confronting him try and open up to him. If he's anything like me he will appreciate the honesty and will be able to understand the human element behind you approaching him earlier.
He's also probably a little hurt right now from what you said earlier. It seems like he's trying his best to be there for you and this interaction you guys had may feel like a slap in the face to him.
Then again, I could be completely off base. These are just my suggestions from reading what information you've posted here.
Best of luck!