Getting people not to knock

I’m getting to the point where I might just buy a giant poster board with suction cups, carry it with me, stick it on every bathroom I go into. Have the poster say In 5 inch letters”I HAVE PTSD AND KNOCKS TRIGGER ME DO NOT KNOCK I ALSO HAVE IBS SO I WILL BE IN HERE A WHILE”

It might be a half truth (I have unrelated PTSD and no IBS) but In the past I have tried fake “out of order” signs with scrap paper and marker and assholes still knock. The bathroom door isn’t the place to educate people on the common but unheard of paruresis, it’s the time to be clear that I need them to F off so I can pee, and IBS is a lot more well known so people will say “oh ok imma just find another bathroom instead of waiting”. I need to stop caring what people think and just do what needs to be done. If having an obnoxious sign gets people to obey and allows me to go to college then so be it.

I still have pee anxiety around sudden noises but that developed after the fear of knocks. If I can get back to just the fear of knocks I think this is what I’ll do.