Fibromyalgia is a condition that includes pain, tenderness, stiff muscle, and fatigue. Researchers want to find out if "a drug" called milnacipran can help people with fibromyalgia. milnacipran (Savella) is approved by the FDA for the management of fibromyalgia. In this study, milnacipran will be given to find out more about how it affects pain and thinking in people with fibromyalgia.