Is my boyfriend gay?

I've been with my bf for 9 months now, and things were going great, or at least I thought so. Last week, I came home early from work, and he didn't hear me. I went upstairs and found him masturbating in the bedroom over something on the computer screen. He tried to hide it from me, but I demanded to see. He'd minimized the screen, but when I clicked on it a picture of a stark naked David Helhoff popped up. My bf was just like, "Yeah, so what, deal with it", then stormed out. When he came back I expected an apology, but he just barged past me carrying a lot of rolled up posters. He slammed the bedroom door and locked it. About an hour later he left the room and drove somewhere. When I entered the room I saw that he'd covered the entire room in David Helhoff posters including the ceiling. This is so weird. I don't know what to think :/