There are book like "Your Symptoms are Real" by Natelson... and that is about Fibromyalgia & Chronic Fatigue, and "It's Not Mental" by Wolfson which is about migraines, halluciniations, many weird symptoms and even depression which still didn't make it "mental!" The doctors insisted the child sleeping so much had to be yet more depression, even though she didn't seem to be depressed.

Personally, I'd get a new doctor.

I'd look for one with skill in Integrative or Functional medicine. And I'd look for any other new doctor that I thought might help.

A co-worker spent a year in therapy and suffered a broken marriage for something "mental" until finally going to Mayo clinic. It wasn't "mental" at all.