There are several articles to read regarding Vitamin D, as well as some case study information on Vitamin D deficiencies in people with Fibromyalgia.
It is important to remember that Vitamin D is NOT an analgesic (pain reliever). And, of course, this information is intended only to educate and NOT diagnose. It is safe to take Vitamin D with medications, from what the documents located at the above-linked URL state. However, please talk to your doctor about how much Vitamin D you should be taking.
Be well, and be well informed!