If I could answer this question medically, I could retire to my own tropical island somewhere in the South Pacific. Unfortunately, I don't have those answers but I do have the spiritual answers as to why you and so many others struggle and suffer with chronic pain of all types.
There is great benefit for you in suffering this pain. God is in the midst of working wonderful changes in your heart and life. This should bring you hope.
As you deal with chronic pain God is revealing your spiritual character to those around you. I know a woman who has battled chronic pain for decades, been in and out of casts and wheelchairs, and could be disabled from her physical pain and restrictions. She fights every day to honor God by how she conducts herself. No matter what shape she is in physically she aims to demonstrate godly character in the midst of it. It is not that she never gets down or sad, because she does. It is that she doesn't stay there. No matter what befalls her, she is always speaking of God's faithfulness and her trust in Him. This is encouraging to others around her and helps her live on the side of victory despite her circumstances.
Do you remember Paul and his thorn in the flesh (2 Cor 12:7-9)? Paul asked the Lord three times to remove it and God said, "No." Paul came to understand that it was more important to God that he demonstrate God's grace in the midst of his pain than it was for him to be free from the pain. God used the thorn (whatever it was) to keep Paul from sinning. In Paul's case, it was the sin of pride he was being protected from. What could God be protecting you from through Fibromyalgia? When you think of your affliction in this light, isn't it something to truly thank God for?
Another reason you are suffering with Fibromyalgia could be the avenue of ministry it gives you in the lives of others. Suffering in a God-glorifying manner makes a tremendous impact on other people! It gives you a kind of credibility that non-sufferers do not have. Ministering to other people while in the midst of your own struggles is a powerful statement of the power of God. I have another friend who has a chronic illness and despite her own pain and trials with it she runs a support group for others. Through the group she is able to talk about the sufficiency of God to meet her needs, His power, abundant grace and how she makes it through each day. This kind of message brings hope to others who need to be motivated and who also need to see that someone really is living in spite of their physical pain. It is very significant to see other people serving and ministering in spite of their own troubles.
We will wrap this up on Monday.