My diagnosis was by my rheumatologist, who explained to me that I had over 11 of the 18 pressure points that were painful when pressed. As spacie_05 said, it hurts everywhere.
There are also a lot of other symptoms that go alongside FMS, the really common ones are irritable leg syndrome, IBS, and when you wake up in the morning you feel worse than you did when you went to sleep. Many others include drug intolerance, depression, allergies, etc. etc. etc. the list goes on and on.
If you are experiencing pain and your doctor does not seem to know, or is treating you like it is all in your mind, then 'change your doctor'. I changed several times until I found one who actually believed me. It took me 15 years to get a diagnosis. So much for the NHS...
all i know of is the pain points test which ***** because you are telling them that it hurts everywhere but to prove that that is what is wrong they have to push on ALL of those points that may already be in pain...I was in tears but at least it helped the doctors know what was going on I guess =?
Currently there isn't a blood test that can diagnose fibromyalgia, but there is a research test on spinal fluiid that apparently can make the diagnosis :
http://www.medhelp.org/health_pages/Fibromyalgia/Diagnostic--Blood-Tests-to-Help-Diagnose-Fibromyalgia/show/377?cid=39