Hi, yes! you can go in for an second opinion for psychiatrist opinion and also a sleep study by sleep specialist who can understand more and treat accordingly. Sorry to know that you have gone through a very hard time since years. How are you doing these days and are you on any medications or been referred for further investigations. Keep updating the section as your thought may benefit others. good luck, take care.
It's possible the part of the body he was referring to is the hypothalamus. The hypothalamus is like a central control for emotions, eating, and sleeping. The entire endocrine system and central nervous system is linked by the hypothalamus.
Mental disorders of the hypothalamus relate to depression, bi-polar and schizophrenia, perhaps that is what he is referring to.
I wonder though if you have any other health issues such as thyroid? I see from your post you have insomnia- have you ever had a sleep study completed? Some sleep disorders present as mood disturbances and are closely linked to other mental health issues.
I had been to numerous doctors who all gave me an anti-depressant claiming I was depressed. My final step was seeking the help of a psychiatrist who told me in fact based on my symptoms and sleep studies I do in fact have a sleeping disorder called Narcolepsy and in no terms did he believe I was clinically depressed or bi-polar. Thankfully to a psychiatrist I am recieving the proper treatment and am not on any depression meds.
I must add that depression is a first line of defense for many disorders because it is true that mood disturbances can create many issues even insomnia.
I hope this helped in a tiny way- Hang in there and keep us posted with your progress.