I've been dx'ed with fibro a long time ago. I always searched for the 'underlying' problem as 'fibromyalgia' by itself did not make sense to my mind.
I searched long and hard and it seems that often fibromyalgia has its roots in adrenal fatige and/or hypothyroidism.
However, most docs/endos are satisfied by merely testing TSH. What you really need to test is FREE t3 and free t4 and TSH. It's also advisable to test vitamin d levels, and b12 and a full iron panel including ferritin (this one is a tad controversial).

It is NOT all in your head. If indeed adrenal/thyroid issues exist and they are addressed, you will see a world of a difference in your mental health functioning.

I am currently addressing both adrenal and thyroid issues and boy what a difference when the endocrine system is working as intended. I have setbacks while tweaking doses and I appear as a mental health case those days.... On days when I get enough adrenal support and thyroid support I am quite a pleasant person to be around.

Please don't let anyone tell you it's all in your head. For the head is connected to the body and they work in tandem. If something is off with the body, the head feels its pain.

BTW, I've been dx'd with lupus as well and most of it cleared up with proper diet and supplements and I guess the adrenal/thyroid support.

Bear in mind that chronic unrelenting stress plays a number on our entire endocrine system and on the HPA-axis. Google will have more info on that.