There still is so much they don’t know about fibromyalgia, including what causes it. I was diagnosed about 30 years ago when I was in my 30s and the doctor said, based on my symptoms, I probably have had it since I was about 19. Mine was brought on by injuries. I’m a bicycle rider.
I’ve found that doing my own research has helped me the most. Sadly, the only thing that alleviates all my pain is painkillers or illegal drugs, neither of which I want to take (anymore). I take ibuprofen, CBD (no THC), and use cold and warm/hot compresses as needed.
Swimming or soaking in a pool or hot tub/jacuzzi is very helpful. There is a great exercise where you get in the water to just below or at your breasts and walk the width of the pool, swinging your arms under water. Anything non-impact is good.
Good luck. I’ve not found a doctor since that first one 30+ years ago who knew much about it.