another intrusive shameful memory popped up. a couple years ago while my family was staying in a hotel, i put the covers over me and took nudes under the covers while my brother was in the room. NOTHING ELSE HAPPENED literally he didn’t see a thing and didn’t even know what i was doing. i just feel so gross about it cause he was in the room while i did it.

Lol I've discreetly masturbated while family and friends were in the room because I was stuck in that situation. I mention it just in case you didn't actually have the knowledge of other people's experiences which are similar in some way- cause I think the fact that that sort of thing isn't discussed can potentially make us feel like we alone. But anyway, the memory provokes shame for you. The best thing you can do for it is let yourself feel ashamed without delving any further into it. It's just the way you're feeling, nobody is saying that you should or shouldn't feel it- feelings are transient, you feel bad for a while, and then it goes away. And that's appropriate, you know? We all have memories which make us cringe. But there is no need at all for it to be a perma-cringe. There's no need for a memory like that to have any power over you or over how you see yourself. So cringe a bit, and instead of replaying the memory or reassuring yourself that you did nothing wrong, just let the cringe happen and then go away again. We OCDers have a way stronger shame response than the normies do, so it probably feels overwhelming and itnense and physical, but the fact it feels physical makes it a great opportunity for focusing on accepting the feelings we call 'shame' in your body, giving them time to exist there and then fade away, without going into the thinking mind about the situation. There's nothing in the situation to solve. It doesn't "mean" anything that's worth your time in figuring out. Let it come and let it go.

there’s also little things that i can’t remember if i did or not like masturbate, but i can’t remember 100% if i did it or not. i never even thought about this until right now.

Welp, if it helps. I have masturbated with my mom in the room. Obviously very discreetly. I was across the room in my own bed, we lived in a studio and I never had privacy. I was a dumb teen. Things happen and there’s nothing you can do to change it. This doesn’t make you a bad person. I am embarrassed but I wasn’t caught or anything. Sex is just human nature.