Chronic headaches are common complain for fibromyalgia sufferers.
There are probably few contributing factors for this, like sleeping disorders (lack of deep sleep stage), unrefreshing sleep that leads to fatigue and depression adds andtriggers the tension headache, and also, some changes in brain chemicals levels).
TMJ is frequent problem in fibromyalgia patients and may lead to tension type of headache, too.

It will be good idea to get a muscle-specific massage therapy on your upper body (there is one clinical study that have determined a positive effect on chronic tension headache by the massage)

Pain-killers and anti-depressants can be beneficial, but, is better to be avoid since they can lead to rebound headache.

Acupuncture and transcutaneous electrical nerve stimulation can be beneficial, too.

Best wishes!
Marija