The best advise I really can give you is that you should tell him. It gets so much harder when you realize you can't tell him because you're afraid he'll be upset that you've been hiding it. I'm sure he'll understand, with villains all over the boards, why you keep it secret. It's hard, even though it hasn't been as long, still the idea you didn't tell him and he'll think you don't trust him, but I think he'd understand.
I really messed up by not telling Rio. It put something between us, this big thing that I could never talk about, and it sucked.