Fibromyalgia:

• A chronic disorder characterized by widespread musculoskeletal pain, fatigue, and multiple tender points that occurs in precise, localized areas, particularly in the neck, spine, shoulders, and hips; also may cause sleep disturbances, morning stiffness, irritable bowel syndrome, anxiety, and other symptoms.
• a condition which affects the muscles and ligaments but does not damage the joints. It is a common condition and can be severe. In fibro-my-algia the fibrous tissues (fibro-) and muscles (-my) are affected by pain (-algia) and tenderness. Fatigue is often the most severe aspect of fibromyalgia.
• A disorder causing aching muscles, sleep disorders, and fatigue, associated with abnormal levels of the brain chemicals that transmit nerve signals (neurotransmitters) It is characterized by symptoms in several body systems

Pain

• a symptom of some physical hurt or disorder; "the patient developed severe pain and distension"
• emotional distress; a fundamental feeling that people try to avoid; "the pain of loneliness"
• a somatic sensation of acute discomfort; "as the intensity increased the sensation changed from tickle to pain"
• afflict: cause bodily suffering to and make sick or indisposed
• a bothersome annoying person; "that kid is a terrible pain"
• cause emotional anguish or make miserable; "It pains me to see my children not being taught well in school"
• annoyance: something or someone that causes trouble; a source of unhappiness; "washing dishes was a nuisance before we got a dish washer"; "a bit of a bother"; "he's not a friend, he's an infliction"

Chronic Pain

• A persistent state of pain whereby the cause of the pain cannot be removed. Chronic pain is often associated with long-term incurable or intractable medical conditions or disease.
• pain that may exist for months or years, rarely causing changes in heart rate or blood pressure but often causing loss of appetite, sleep disturbance, and depression

Any you want to add?