Fear to poop

You should tell them you have this issue, and maybe seek treatment. And maybe warn people beforehand of going to the toilet in case anyone needs to go first who will use much shorter time. That is normal when you know you will be there for a while. But dont avoid going to the toilet for longer periods, that may even make things worse

Could be food intolerance (especially gluten, but also other things), not drinking enough, holding it for too long in the first place, or either way too much or too little fiber that is causing it.