I have had FMS for about five years. I don't think anyone knows what causes FMS, but as Ree4tu said, most physicians/scientist believe it can be triggered by infection, stress, or physical injury. With that in mind, it makes sense to me (and I'm not a doctor or scientist) that the trauma you went through could have triggered FMS. It would probably be impossible to prove, though.
I believe a variety of things can trigger fibromyalgia and it is different for everyone. Usually an infection, emotional stress and/or a physical injury are factors.
Ree4tu