I really believe that for some of us, something happens to make the brain just freak out and start interpreting pain signals in a wacko manner. I think a contributing factor for me was going through a year and a half of terrible migraines with almost no medicinal relief until we finally hit on a drug that worked to prevent theml Just way too much pain. I think pain begets pain. It is a weird story, though, and I've learned not to tell doctors because they act like I am crazy.