Do guys really actually jerk off into condoms or did I get cheated on?

Okay so I(F23) was at my guy’s(23) house, decided to clean up his room cause he was working really hard on a car for somebody and I knew he had had a really full on few weeks at work so I thought I’d help clean up a bit since his room was dirty as well, like I would NOT bring someone back to that, looked like a bomb hit it, clothes everywhere, plates and cutlery and shit from the other night and a pile of dog hair on the ground, I was picking up beer bottles and rubbish and other crap when I found a condom wrapper on the ground. We’ve been exclusively sleeping with each other for over a year and I have an IUD so I was obviously suspicious, but I put it to the side for a second. I know that teen boys jerk off into condoms, I know it’s a thing people do but I still couldn’t help be suspicious even though like I have no idea when he would’ve found the time to do that like he already struggles to make enough time for me, and when he does he usually cleans his room…I asked him if he fucked someone else and he like laughed and said no of course not he was just jerking off into it. I believed him but am I being naive?