Fibromyalgia Pain, Don’t Worry We’ve Got a Strain : Fibromyalgia is thought to be a nerve disorder that causes widespread body pain and fatigue, as well as other symptoms. For the most part, it’s unknown exactly what causes the disease. Until recently, it was said that the pain and fatigue was all in the patient’s head. Today, fibromyalgia is a recognized disorder that is commonly treated with pain medication. But, there’s an alternative.