Unfortunately there are a ton of unknowns,but I will not argue with success.It is quite possible that chronic stress,trauma(physical or emotional)can provoke change in microbiota compositions.
There is the brain stomach axis,which is linked by a second brain(your gut) and I believe that the microbes play the role of being the button pushers of your immune system,so to speak,and 95% of our seratonin is made in our gut,which would explain why depression is almost guarenteed in fibro patients.
We all have a different set of buttons that control everything in our wildly different microbiata components.That is why,I believe,we all have differences between our illness symptoms.No one knows how much we ingest that damages us daily.
The other point about not having illness,thus no major meds in your pasts,the only thing that I have come up with is that generally women take better care of themselves and go to see doctors more often.They also have more infections,because their lady part has its own microbial set up,they suffer from UTI's,I have not read up on it,but are they not treated always with antibiotics?
I am guessing that that is why more women than men have fibro or it can be as simple as women are predisposed genetically or suffer disruptions easier because of complex hormonal systems compared to men.
I can't stress the importance of reading the many sites that offer info,google FMT treatment for fibromyalgia,there is a site that discusses a man who says he was cured after 6 different donor enemas,over a few years.I dream of being the second,and I do not know if it is our holy grail(hidden in poo!),but I intend to find out!
Besides,after the first time,you get desensitized to the procedure,because you know what you are getting back in return,your life!! There was a reason I kept quiet,most people think I am nuts but I must say,I would rather be considered nuts than suffer from fibro,without a doubt!