First of all stop taking hot water bag every where and every day, make routine exercise schedule and get it checked with physio weather its a genuine disc pain or muscular pain around your para spinal muscles... as you said you are diagnosed with fibromyalgia you should get into routine of exercises to get rid of pain cycle developed... thank you and use cold pack as much as possible...

Yes possibly. Consult your doctor. Check Vitamin D levels. Physio will help for back pain. Drink plenty of water to avoid dehydration because dehydrated disc is more prone to injury