Disability. Pain is an objective complaint that is often poorly understood by others and is frequently poorly explained by the sufferer. Its cause may not be obvious in a lot of cases, creating fear, medical attention, extensive and expensive work up and sometimes treatment. Economic and emotional repercussions are substantial.
Wow..tough question. The mechanisms of pain are too plentiful to even discuss. There are also so many types of pain, and effects of pain- emotional, mental, physical. If you are talking about pain in general, maybe it is fibromyalgia. Hard to say. Need to see a doctor and go from there.