Im someone who has had chronic fatigue immunity dysfunction sydrome (severe case) for the past 13 years and on looking about this fibro section, I can see that many of you actually have undiagnosed CFIDS. http://wwcoco.com/cfids/bernesx.html
A quarter of those who have fibro end up developing CFIDS (CFIDS can start off as fibro). The statistics going the other way are about 75% of those with CFIDS have fibro as just one of its symptoms. Many (most) doctors are not good at all at knowing the difference of these things and how they interelate.
So how does one tell the difference??? Firstly..pay attention to your history eg those who get ill after mono or EBV are more likely then not got CFIDS (10% of mono cases develop CFIDS). CFIDS is often triggered by viral infections...
(both CFIDS/FM and FM alone, can share same kind of history for such things as the illness developing after an accident or physical trauma so that kind of history will not help to distinguish but a viral history or viral symptoms can help to distinguish).
Fibro does share some common things with CFIDS eg both illnesses can get headaches/migraines, brain fog, irritable bowel syndrome, Interstitial cystitis, fatigue ... or also have hypothyriodism connected to them. So those things will not tell the two illnesses apart except the degree of exhaustion often can.
CFIDS/CFS/ME exhaustion can be to severe degree at a completely different depth to someone who only just has FM. Not only pain stops those with CFIDS from being able to work but also the severity of the exhaustion and weakness (and other symptoms too). CFIDS people may spend a lot of time laying down or in bed.
Exercise will often help those who have only FM but if you have CFIDS with it, you will find that exercise often makes you much worst!! With CFIDS, one of the defining features is post exertional malaise eg you do something one day and end up much sicker due to doing that, the next day.
In CFIDS, there may be noticable immune dysfunctions.. eg fevers, swollen glands... viral like symptoms.. (this isnt the case with just FM)... and many other symptoms which are not usually found in just FM.
If you have CFIDS/CFS/ME find yourself a medical person who specialises in this, who is knowable and specialists in this illness (not someone with a psych biased as those ones dont have a clue!!).
thou you cant cure CFIDS.. there are things which can be tried to help the symptoms and to help all the coexisting conditions and symptoms you may have with it eg treating coexisting POTS, taking a medication such as Klonopin (to help balance the nervous system as in CFIDS there is often overactivity), B12 injections of hydroxocobalamin etc