I don't have fibromyalgia, but I have pcos and endometriosis. Inserts for your shoes are a MUST. Idk what your SSVs or SM are like but talk with them about it. Make sure you get all of your breaks. If I didn't fight for my 10s they'd never give them to me. I have two very nice shifts that try to give me an extra 5-10 min break if I am having a really bad day with pain management.

I try to stretch before work (rarely happens tbh bc I forget to). But after work I stretch at home. I have an electric heating pad for my back and stomach. And taking hot baths occasionally helps too. I found that taking extra steps outside of work/after hours helps keep my body from being in too much pain the next day.

Most importantly, have documentation of your health problems (i.e. doctor's notes for appointments or if you ever call off. Or just a doctor signing off in your diagnosis of a chronic illness.)

And find out what works best for your body and health. Before my surgery, I was working short shifts (4-5.5 hours 6 days/week. Only 4 days/week immediately before the operation) because standing became too painful. Now I can work 8.5 hour shifts, but I need a "recovery period" so I only work 4 days a week.

Don't feel bad for having stricter availability. Taking care of yourself long term makes you a better, healthier, and more productive employee.

I have really nice adidas shoes with foam soles, lidocaine patches, and when things get really bad I bring my tens unit in for breaks.