I don't have fibromyalgia...I have post polio syndrome. My left side of my body is weak and mobility is limited. However, strengthening exercise is a true healer when it comes to pain and as such, even though my low back, hips and neck are very arthritic, I have no pain as long as I continue to keep those muscles strong. When they weaken, pain increases.
Proper assessment is key though otherwise doing the wrong exercise or using improper exercise technique can ...and will make things worse.
Have you asked your Doctor for a referral to a back clinic or physiotherapist to get a proper assessment and exercises to do? No side effects!!