I had the exact same thing. Excruciating lower back pain that radiated thru my hips and down thru my legs. I ended up finding out that it was not due to my fibro but actually due to my pelvic muscles spasming, which you can't even feel. Because of the spasms, things started rotating and the spine and hips kind of followed which is why I had such awful pain. I'm in PT for it right now. I've been having this issue for a year and didn't know if it was the fibro or part of the endometriosis. I luckily had an awesome endo specialist I just started seeing who referred me to physical therapy because he could tell upon physical examination that my muscles were spasming.
I would make sure to ask the doctor about
your symptoms, just to be safe. You don't want to blame everything on fibro but it's also hard to know when NOT to.
Hope you have a comfortable day
Kathy