I don't know what to tell you to do, but I just wanted to share that I understand your question. My husband is disabled in a not visible way that seriously limits his physical activities. No one knows about it unless we tell them, and even then, they still don't understand how it limits what he can do and/or they keep forgetting, and I have to keep reminding them... "no, he can't help you with that", "please walk slower, we can't keep up with you," etc. Even my brother and his wife (after years of my husband's disability) still don't quite get it. They want to, they just can't fathom it, I guess.
So, like you, I always wonder, should I tell people? Should I keep reminding them? No one minds when I do tell them and they are always gracious about it, but I always wonder if they get tired of hearing about it and think I am trying to get attention.
I guess my three pieces of advice are this...
1. I think people really do care.
2. No matter what you tell them, they probably won't really get it and will need constant reminders.
3. If you can, try to find a support group, maybe there's an online support group for people with autoimmune disease and they can give you good advice regarding the social aspects of dealing with it.
I'm sorry you have this illness. I can't imagine. Always remember to turn to God for strength and comfort. He cares always.