Fibromyalgia (FM) is a health condition that causes widespread pain and tenderness. It is unclear what causes FM, but your body becomes very sensitive to touch and temperature changes in many areas, especially muscles. There is a wide range of symptoms involved with FM. This can include disrupted sleep; ‘foggy’ brain where it is hard to think properly; you are more prone to depression or anxiety; and sometimes your bowel and gut functions can also be affected.