Don't let anyone make you feel that way! You have a legitimate medical condition. Hold your head up high and smile, smile, smile even if it kills you. They do not sit in judgement of anyone. You're not doing anything wrong.
I have chronic pain and it got to the point when I was dropping off prescriptions, the pharmacist would say "Hi Pam!" before even taking the script out of my hand. He knew me by sight because I was in there so much. I was horrified so I just made a joke of it like saying something like "geez, I feel like I live here, I'm in here so much!"
There were a couple of the girls who work there that give me that look but you know what? Too bad.