What are the rules for sharing a bathroom with people who aren't allowed to?

I have the upstairs bathroom and everyone uses it and doesn’t replace the toilet paper and I got hell for hanging my boxers up to dry on the shower curtain rod… This person has her own private washroom and doesn’t stop anyone from using my washroom… People in the house have Head Lice and Scabies and they refuse to use their own bathroom, people just avoid the bathtub in the basement and use mine, because it is cleaner… So I just took out my towels and toilet paper and war is brewing.
What worked for you?... I seem to wash after neighbors who use my bathroom without remorse and they do it right in front of me.