Its basically something that happens over time as a result of other things. Such as... not getting enough exercise... not sweating out impurities in the body or drinking enough water.
Before i sat in front of my computer all day I was a bodywork therapist and had a few clients diagnosed with it. One woman didn't do much for it and barely could take any touch from me.. and so canceled the sessions. I heard later she was doing much worse.
The second woman, started going to a gym every morning to walk on a treadmill & do some light weights. She changed her eating to un processed foods and added a lot more water to her dailiy intake. She had to change her brands of makeup and lotion because some things just bothered her skin so much and when I started to give her massages I could barely touch her and sometimes had to do it through a cloth so it wouldn't bother her skin as much...
After a year of a massage every week, working out & eating better she was undiagnosed with it...
After knowing about 8 people who have been diagnosed with it I have sort of come to the conclusion that its more of a lifestyle thing.. like .. if you sit at the computer all day every day and not exercise you will eventually start getting aches and pains in your back and your neck... and probably some other places..
Fibromyalga is just the same kind of thing but it usually takes years (its not a young womans disease and men won't complain about stuff like this to a doctor generally)
Your muscles get stiff to the point of drying up & it inflames your nerves making it hard to be touched anywhere..... and will only get worse..
best thing for them is healthy eating.. lots of water.. movement.. wallking.. stretching and sweating every day & hope
Good luck