Fibromyalgia is one of the most common diagnoses in patients with chronic, whole body pain.  After many years of treating whiplash patients, researching the subject, performing clinical trials, and using just plain common sense, it's a DOE.  A DOE is a "diagnosis of exclusion".  This means that when the doctor doesn't know what's wrong and has excluded everything else as a possibility, they use a DOE.  When a patient has "whole body pain" and seems to be tender everywhere, it's often labeled "Fibromyalgia"  What does this mean in doctor speak?  Muscle Pain. 

In my experience, very few chronic whiplash and whiplash associated disorder suffers have Fibromyalgia.  Instead, they have pain in multiple places that can all be easily explained with the right level of knowledge and experience.