Thisstar-I have most of my FMS pain in my legs and lower back. Many times I feel the same pain you are describing. I didn't want to move. I could barely walk to the bathroom the fatigue was so bad. I know pain killers will help but what I have found to work for me LATELY (I just started this this weekend), is walking just a little bit and then work your way up to more minutes per day. Don't overdue it. Just do as much as you can tolerate it. Last Wed I actually attempted work and paid for it in leg pain for days. So on Sat I tried walking just a little bit in the mall. This was of course with the help of pain meds. Sunday, I went swimming. I had to rest due to the fatigue but, overall I felt OK. Aftwerwards, I was sore like I had worked out and I did have to take something for pain to get to sleep. But, on Monday the pain was so much less severe. It was only in my knees. Monday and today I went bike riding. This morning I woke up with NO PAIN! I absolutely can not believe it. They exercise is the key but when you are hurting so bad you can't think of anything else. I know where you are coming from. I feel your pain. Try to hang in there.
Have you tried taking Magnesium? I find that helps me! Maybe you too!