Wow. That is so cool to hear that something so simple and natural as sunlight could help ease your Fibro symptoms. I totally know what you mean about the symptoms worsening during your period. I think what I have is the very early stages of Fibro, and yes.. the pain just before and during your period can be pretty horrific.
It almost feels as if your muscles in your whole body are going into one HUGE spasm.
Seems funny now, but the first time this happened I really thought I was dying!
I found that the source of the pain wasn't from my uterine area, but actually from my lower back area. Not too sure what that means yet, but last month I began drinking lemon juice squeezed in water 3-4 times a day and I had no pain before & during my period whatsoever, which was great! And for the first time in a while my flow was painless AND bright red right up until the last day of my period.
Maybe I need to move to a hot country to be free of the rest of my symptoms. In the meantime, I'll try to make use of the 4 weeks of sunshine we get here in London at this time of year!