Hi, Nuria, and welcome! I'm so sorry for all that you have gone through and are going through. That sounds horrible. I hope your doctors are giving you pain relief until your knees heal.
Part of your problem could be that you most likely aren't moving around a whole lot and that is understandable with having the knee surgeries. Gentle exercises like walking and swimming are wonderful for fibro. They are easy on the joints, too. But, I'm not sure when you have knee replacements. Talk with your rehab specialist about it. As soon as it's fine for you to start moving, do that. Start out slowly and build up to a routine. When I first started walking, I could only go about four houses down and had to turn around. Now I walk my dog first thing in the morning for 1 to 1 1/2 miles and then I do a lot more walking in my home, shopping, etc. This makes me feel so much better, gives me more energy, and helps with a good attitude. I'm sure that sounds impossible to you right now but when you totally heal, I think it's possible. My aunt had two knee replacements and when she healed she was doing everything she did before the surgeries.
I use malic acid/magnesium supplements to help with pain and fatigue and I also am deficient in vitamin D. Since I have started with these vitamins and supplements, I have been doing much better with the pain.
Sleepless nights are very common with fibro. I had an especially bad night a couple of nights ago. I was exhausted but as soon as my head hit the pillow, my eyes flipped wide open and that was that. Pain can wake me up, too, but not usually because I now have it pretty much under control.
Be sure to check out Fibro 101...the second thread on the forum. There are links to good information about fibromyalgia, including links about malic acid/magnesium supplements and vitamin D and how they work in our bodies. You will learn a lot on that thread.
I suffered from lower back pain for years. Your pain could be from lack of using those muscles or from carrying yourself differently with your new knees, I would imagine. But, for me, learning how to get in and out of bed and in and out of a car helped me a lot. Here is what I do.