I'm starting this response with the assumption that you've been screened for brain chemistry issues, thyroid problems, or uric acid crystals accumulating in spine (cause of gout in big toe joints).
My response will be esoteric. You want Western medicine, stop reading.
At the end of all this, I'll have some suggestions for you, but it's going to take me a while to get there.
When I was young, until my early twenties, I suffered cycles of a black depression. Numb, feeling completely hopeless, the whole nine yards.
When I moved in with some roommates, I was at a very happy moment during dinner with them and experiencing intense waves of energy coming out of my heart and down my arms. That kind of experience was normal for me.
My roommates noticed something happening, so I told them what I was experiencing. That was the first time I learned that other people didn't experience an awareness of the energy flow in their bodies. I never knew. Not a clue.
Not long afterwards, I was off on my own and decided to practice some yoga, including something called bellows breathing. I soon developed a routine of doing bellows breathing 3-4 hours a day.
I discovered I was on an 11 week cycle. At the high end of the cycle, with each bellows breath, a pathway in my energy body would experience an increase in the energy flow.
What I discovered was that my energy body - head/spine/limbs - was severely restricted. But over several weeks of the high end of my cycle, followed by what I called semi-highs, doing the bellows breathing would pick up the energy flow in a particular part of my body, say the arms, legs, chest, back, or trunk.
Opening up these restrictions would also cause the muscle in that body part to jump, unwind, and release tension.
When you consider the energy body, think of the head and spine as 220 volts, and the major nerves running down the arms and legs as 110 volts. In general, major nerves in the body also reflect major energy passageway. Where major nerves come out of the spine are also major energy centers (also called chakras)).
Over the course of the year I opened up the restrictions in the energy flow all over my body and head.
When I did that, my black depression lifted and went away.
I realized the restrictions in the energy flow in my body caused my depression.
I discovered when I was sick during that year, the aches and pains I experienced were restrictions in the energy flow. When I lifted that, my cold was a slightly runny nose but I felt fine.
Here's the catch. My energy body was a reflection of my thoughts. My patterns of thought created patterns in the energy flow in my body, which fused with my muscles. A feedback loop in a sense, and why it took so much effort to lift the restrictions. My thoughts tended to re-create the restrictions in energy flow again.
At the high end of my cycle, when I did the bellows breathing, pathways of energy would 'light up' part of my body, my back for example. I would experience/see all the energy pathways.
I came to see my mental landscape as like a cloud shot through with constellations of stars. The stars reflected intense thought patterns, with similar patterns creating constellations of stars.
The more powerful the thought, the brighter that star. The brighter the star, the more powerful it broadcast that thought, or patterns of thought.
And since the energy body is a reflection of thoughts, thoughts have a way of fusing into the muscles, holding thought patterns in place.
During one high end of my cycle, I was able to get to a place where I had awareness of the energy behind a particular dark thought star. I was able to drain some of the energy that powered that broadcast. Didn't end it; I thought at the time I could make my way back, but that didn't happen.
The interaction of thoughts/mental landscape, energy body, and physical body are part of what makes us who we are and maintains our personalities into particular patterns.
Exercise can help open up energy channels in the body, which is a reason why exercise can help lift depression.
I'm going to jump ahead, but I'll get to my recommendations for you in just a moment.
20 years later I did therapy and I was advised to do 12 Step Groups. I ended up doing five a week. With plenty of quiet time, I started visualizing a current of energy running from my spiritual eye (central forehead) to my medulla oblongata. Think of the shape of this visualization as like a banana. When I breathed in, I drew a current from my forehead back to my medulla. When I breathed out, I visualized the current going from my medulla to my spiritual eye.
After a time, I could feel the current.
After doing this for six months, one side of the major band of current that runs around the crown rolled, unleashing creative energy and insight. Next cycle, the other side rolled, then energy pathways opened up down my face. I then had higher currents of energy running through my head/brain. A not always enjoyable process until those channels opened.
My suggestion for you is that twice a day, morning and evening, you do bellows breathing for five minutes. This can help settle your body and mind. Then you do five minutes of visualizing that current of energy from the spiritual eye to the medulla, back and forth.
During the day, if you attend a meeting that doesn't require your complete attention, practice visualizing that current, back and forth.
If while during this, you feel a knot developing at the back of your head, that will be a restriction in the energy flow over your medulla.
If you find a knot there, you'll probably have restrictions in the energy flow in the rest your body, and that will be a cause of your depression.
At that point, I suggest you find someone who can guide you through doing energy body work to help you lift the restrictions in your body and spine.
If you discover other sore spots in your spine, those will also be major restrictions.
That's my suggestion for you. This will require you turn some of your attention within.
When you do, you might have unusual experiences. Think of them as information. You also might experience dream like states while conscious. Again, consider it information. You'll be learning about how your mind and body work together.
Also, if you want to talk to someone about your experiences, I suggest you do that with a person who has an interest in inner experiences. I also suggest you don't do this technique around others. Anything with an inward focus can seem uninteresting to a sign of mental derangement to a person with a fixed, outward focus.
This might not be the path for you. I don't know why it was the path for me. I can only suggest it might very well be worth the effort for you to try.