My high school sex ed never taught anything gay or anal. So I knew to wear a condom with my first girlfriend, but until I was a freshman in college (a year ago..) I didn't realize it's important to wear one with a guy too. First gay experience, we'd been seeing each other for a month and I thought I was pretty ready, sock on the dorm door and everything, but then bro asked me if I had a condom and I was like "huh?" And obviously I didn't so he just gave me head instead
For whatever reason I thought condoms only helped in vaginal sex, since that's the only thing they taught its use for. Didn't really know how gay and bi men prevent STIs other than monogamy and a few other assumptions. Part of that stupidity was probably just me being optimistic and horny brained about not having to wear anything