Public restrooms
I refuse to use public restrooms. The toilets are always disgusting no matter where I go. Blood and other excretions are always smeared on the walls, toilets AND door handles and there are large insects stuck to the walls and they're every shade of disgusting. This often means I hold it for several hours, dehydrating myself so I don't wet myself or create an emergency where I have to use one. I often have to go straight to work from school, so I don't know how I'm going to function with my new life schedule anymore and I'm having difficulty adjusting to apocalyptic proportions.
Similar to you I suffer from hating small spaces and public toilets are the main culprit, they send me into panic attacks and I have to hold it in too, over the years I've got used to it but I'm not finding it easy with being at uni all day.
I'm in community college and it's rapidly destroying me. The anxiety I get from simply the concept of school shuts down my parasympathetic nervous system and I find myself having digestive issues (at the risk of TMI: constipation-chronic or functional, etc.) and just being in the social setting terrifies me to a point where I want to burst into tears or scream. Is it that bad for you?
This sounds like a serious thing. Are you afraid only from public restrooms or from any small place such as elevator for example..?
Elevators are fine. I just have an intense, phobic dread of public restrooms because of their condition and the lack of sterility. It's quite nauseating.
Then it does sound like a phobia, because it's seriously ruining your daily life.
I can highly recommend you this:
https://www.anxietybc.com/sites/default/files/adult_hmspecific.pdf
https://www.moodjuice.scot.nhs.uk/phobias.asp
It is really helpful. If it doesn't work, maybe contacting the mental health professional would help. :)