I don't understand why you keep going on about the sheets. You made a thread about this when you were 14. You had advice on how to avoid getting your sheets and mattress wet, you said you'd tried it, and you said it worked (and of course it worked, it involved buying and using standard commercial products). It is a solved problem. It'll be an even easier solved problem at university since nobody is going to care less what you put in the bins or when you shower.
I get that it's annoying and time-consuming and potentially expensive. I get that you'd much rather it stopped. I don't get the obsession with a nonexistent consequence. If part of the problem is that you can't stop obsessing over getting your sheets and mattress wet even though that's been a solved problem since mid 2020, then tell your doctor that.