Hi! I also have fibromyalgia. I've found that (at least for me) it's not always about the job, it's about the understanding or willingness to learn of the people who employ you! My first job was at Panera, and it was awesome! The people there worked with me. But then I had to transfer to a different Panera, and it went downhill and I couldn't work there anymore.

Any kind of work at home job. I work with adults with special needs. The ones I chose to work with don't need physical support so I just drive them around and hang out and help them and it's really easy

Aldi let's cashiers sit

A receptionist position might work for you. It's not high stress and is something you can sit or stand to do. It also doesn't require a degree.