https://www.fibromyalgiafund.org/why-fibromyalgia-muscles-hurt/
Check this research out. I found it very descriptive. Essentially, though, it goes back to square one when I was diagnosed 45 years ago. My meds then were low-dose Elavil (I took the generic) for stage 4 deep sleep, Naprosyn (anti-inflammatory), Parafon Forte (muscle relaxer, I take the generic).

Now that I’m 77, I can no longer take Elavil (hallucinated after 5 years) - use C-Pap machine that doesn’t make me feel rested; can’t take Naprosyn or anti-inflammatory drugs - had internal bleeding a few years ago; still take Parafon Forte - can take this muscle relaxer for a couple days at a time - split 500 mg dose in half…puts me to sleep, makes me groggy, take on as-needed basis only.

Always tired, more muscle tightness - have had two UTIs - each one, muscles in area of uti clenched and wouldn’t loosen up for months. First UTI it was my left hip. Second UTI, it was my left flank.