He acted gayish but insists that he's straight, what do you think?

[Sirius]

We're two guys in the dorm and I know he's straight until this happened..Last evening he went to a party so I was alone and watched porn for a while. I didn't know what time he would be back so I was doing my "thing" when he entered, I was kinda embarrassed and told him I'm sorry for that, he said it's fine and all. I didn't continue it and just tried to sleep while he was fixing himself for bedtime. Then the next morning.. He normally wakes up earlier than me so I was about to wake up and change (it was a double deck bed, I was on top) but I can't find my shorts, I thought it fell off the floor..and I thought he already left but when I went down lol he was doing his stuff wearing my shorts. The same shorts I used when he accidentally caught me the last night. I was like wtf are you doing with my shorts dude are you gay? while he was trying to hide everything with the blanket and saying no he's isn't gay and that he's staright. I was at the wtf mood so I just went to shower already. When I went out he was already gone with my shorts at the laudry basket. And then I post this. It's like 10am and I'm waiting for him to come back. What do you think about the situation and what I should tell him and stuff?