There are so many things it could be. Getting some blood work, x-rays, MRI, etc. Is a good place to start. Fibromyalgia is a rule out diagnosis. It can also affect different people in different ways. When I have flare-ups I tend to feel generalized deep aching most places and my arms and legs feel like lead. I also tend to feel like my thigh muscles are burning, almost like way overexercising them. Just a general observation but it seems like people who have one chronic pain issue very often develop another. I've had fibro for 13 years. Then I had a joint replacement in my thumb from arthritis. The implant failed and I had 8 more surgeries and wound up developing RSd/CRPS. Diagnosis of some chronic pain conditions can be a long time coming, so don't give up, even if they can't find an answer right away.
Sorry, hit post before I finished. Have you had x-rays and/or MRI? If not, then I would ask for those as well. Good luck to you.
I would also ask for blood work to check for rheumatoid arthritis.
You might have whats called fibromyalgia, as well as other things wrong (like your back problems). Fibromyalgia is general pain throughout your body I think (in "regular people" terms!). You can find out much more if you simply do a search about it on the internet, or look and see if there is a group here on medhelp! Good Luck,
shinty