I haven't been on here or messaged for a while. Yesterday I did indeed use a disabled loo in an emergency situation. For all the reasons you state re privacy people who suffer with our condition are actually disabled by it. And by definition I think there is a real need to use such facilities when required. My situation yesterday has prompted me to visit the messageboard again today to get reassurance from others. Because although the incident is now passed I still find myself reliving it in my mind.
Like you I didn't go to university, don't holiday with friends, or sleepover, limit my days out and really live a half life because of this anxiety of going to the toilet in places other than home! I hate it. Every day is another challenge to try and overcome it. I have anxiety problems too and take medication for it but have this year finally stopped taking antidepressants, so hope to be going in the right direction!
I don't know what the answer is, but I do have every sympathy. Hope this helps you some.