For me, they've always gone hand-in-hand... and worsens during times of extreme stress.. I am continuously mindful of not getting overly involved in anything - even though it is my natural instinct to try and help where I possibly can...

As far as a diagnosis they are different and CFS is mostly about fatigue and Exhaustion. Like myofascial pain syndrome if you have one you are more likely to get the other but its not set in stone. I have all 3 MPS FM and CFS with seratonin syndrome meaning I cant take entire categories of medication.
Here s a great article talking about the research into fibro and the chemical changes in the brain and so on http://arthritis-research.biomedcentral.com/art...

I have fm, CFS and ms which my Dr treats as a package, hard to tell tho sometimes what symptoms are my ms and which are fm, just found out though that my illness goes back to when I was 4 caused by trauma x

CFS and fibro go hand in hand. I have notice a more extreme fatigue than usual and can't get enough sleep. Here are the symptoms of CFS
The person should also have one or more of these symptoms:
difficulty sleeping or insomnia
muscle or joint pain without inflammation
headaches
painful lymph nodes that are not enlarged
sore throat
poor mental function, such as difficulty thinking
symptoms getting worse after physical or mental exertion
feeling unwell or having flu-like symptoms
dizziness or nausea
heart palpitations without heart disease

Hi Jo I believe FM ME and Cfs are related they all seem to originate from our brain sending messages of pain our body react accordingly, Inturn the physical impact of lack of sleep pain create the perfect storm that's when I believe our bodies cannot cope hence the chronic fatigue. That's my take on my situation rightly or wrongly it helps me try to get through the day.