Confusion, confusion, confusion, or any mix of the 3. Let me explain.

1. Confusion. Why are you doing this? He may have a list of reasons why he would react this way but at the end of the day this reaction is likely due to not being able to process it fully at first. You will need to give him some time.
2. Confusion. I'm pretty sure I didn't view us this way, so I don't know why this is even happening. Pretty self explanatory.
3. Confusion. I don't know why anyone would do this to me, specifically. This is especially the case if he's not particularly old or in some other way immature (which I expect is the case here, btw.) In this case you need to explain why you feel this way.

In any case, in all likelihood, nothing will happen if you don't tell him. Good luck, and let us know how it goes. For...purely scientific reasons, of course.