This has a bit of technical jargon, but i find very interesting the idea proposed that sustained pain somewhere in the body might be the monkey wrench that kicks starts fibromyalgia. See the link followed by an excerpt. In my case, that would fit because I had very bad back pain for weeks/months before the fibro. Or, could it have been the beginning of the fibro? Don't know.

http://www.medscape.com/viewarticle/738462_4

Several researchers propose that regional or focal chronic pain might produce the sustained noxious input that results in hypersensitivity of the central nervous system (Bennett, 2005; Lidbeck, 2002; Staud, 2007). This hypothesis proposes that longstanding bombardment of spinal cord neurons by A-beta and C fibers as a result of ongoing focal pain conditions gives rise to the neuroplastic changes characteristic of central sensitization (Meeus and Nijs, 2007; Nielsen and Henriksson, 2007), making regional pain conditions a possible instigator for the altered pain processing of FM. In fact, it has been proposed that regional pain syndromes precede the development of widespread pain in most patients with FM (Nielsen & Henriksson, 2007). This proposal is supported by the fact that FM is frequently associated with several focal pain conditions that also have evidence of being characterized by altered pain processing, including TMD, IBS, IC, headaches, back pain, and neck pain (Staud, 2007).