Hi Stefanie, I have both UC and IC. (Mine is pretty severe. On chemo drugs for it. Thus, why I am so thin.) I carry a Restroom Access Card with me and explain to people that I will have to access the bathroom often and urgently. Most people are understanding. Some will switch seats with me.
I recommend you get one if you don’t already have one.
Either way, I am amazed at the lack of compassion in these comments. I didn’t choose to be a skinny chic with two autoimmune diseases nor did larger people choose to be large.