If you don't feel comfortable telling him, you don't have to. It doesn't have to be as big a deal as 'coming out' to him, though. The first day I moved into my flat with a group of complete strangers we all sat in the living room, had a few drinks and just got to know each other. I think if you find yourself in a relaxed environment it'll be a lot easier to just tell him, if that's what you want to do.
