Oh can I relate!!!! Public transportation was a NIGHTMARE for me. I had your EXACT thoughts - always. People would see me coming towards them and cringe as I took up enough space for close to 2 people.
All seats were truly a nightmarish experience for me and brought on a lot of anxiety for me. Hair salon, dentist's chair, picnic benches, restaurant booths, movie theaters, lawn chairs, beach chairs, outdoor plastic chairs, folding chairs, school auditorium, teacher parent conferences - you name it - if there was seating involved - it was a VERY unpleasant experience.
It is still one of my biggest joys - to be able to fit into every seat with room to spare and to never, ever, ever have to worry about taking up more than my fair share of space and never, ever, ever having to worry about breaking them.
I am once again reminded how this journey, this lifestyle is SO worth it.
I am very happy for you.