I was raped by my friend last december and I wasnt sure that it was rape either. But even tho you knew him it was still wrong what he did. I know that its hard and you dont want to have him arrested and I didnt either. I didnt report mine and i regtret it now. He needs to know that what he did was wrong. You shouldnt be his friend anymore. If you are still his friend and you dont tell anyone that is like giving him a free pass to do it again.
I know its hard but you need to either report him or at the very least not be his friend anymore.
If you need to talk feel free to
PM me anytime.