Fibromyalgia and autonomic central SYSTEM,why do I have hot and cold flashes? Is it the fibromyalgia or theo?

Is it the fibromyalgia or is it the autonomic system? What tests do I need to ask for. I get hot and then I will get cold. I had a hysterectomy 10 years ago. This really bothers me at night or anytime Im not under a fan or dont have a blanket near me