One thing new research has found is that people with Fibromyalgia have many more pain nerve endings than normal which again will likely be contributing to the increased pain levels.
I too have Ehlers-Danlos Syndrome and what I deem secondary Fibromyalgia. (Diagnosed, but I mean I see it secondary to the EDS). I have had no physical trauma as someone mentioned above, but I have had long-term chronic pain from the EDS and I think after a long time my brain doesn't know how to deal with and the pathways get so worn the pain signal fires when it shouldn't.
I have a lot of Allodynia, which is when your body gives a pain response to something it shouldn't - for me things like clothing, labels, or even an unexpected touch causes physical pain. I also have hyperalgesia, where I feel more pain that should be normal. I.e. if I bump myself it will throb for hours. Both these things are very common with Fibromyalgia and chronic pain conditions.
More women do have it than men, but it may be to do with structures of the body. For example Ehlers-Danlos Syndrome is 50-50 between men and women but women tend to have it a lot worse due to structural differences in the body.
I also think a lot of people are diagnosed with it who actually have an underlying cause, but many doctors will just stop there instead of digging deeper.
The fatigue is utterly crippling. It's NOT tiredness, it's like needing to sit for an hour to try and get just the mental energy to think about getting up to get a drink.
A good thing for all able-bodied people to read is The Spoon Theory. It's one way of explaining what it's like living with low energy.
butyoudontlooksick.com/articles/written-by-christine/the-spoon-theory/