I have GBS /CIDP, diagnosed by spinal tap. They injected my spine with a dye I turned out to be allergic to, so learned to walk again. GBS is an inflammatory disease of the central nervous system, like something shorting the whole house electricity supply and an electrician putting it all back wrongly. My reflexes were reversed, which also helped the diagnosis. If it starts in the feet/legs you have a chance of survival. If it attacks the nerve supply to the heart, it is death, unless you are able to be put on life support. I didn't, but it has been hairy a few times.
CIDP is the chronic form. There are so many ways doctors can diagnose the many diseases of the central nervous system.
Most neurological conditions can be diagnosed. Many of the OP's symptoms are easy to treat. I have suffered many of them, and the suggestions I made work for me. It doesn't involve much money, so worth a try.
Depression is a symptom of underactive thyroid gland. They diagnosed that at the Hospital for Nervous Diseases in London. Once I had the thyroxine I wasn't depressed. They also diagnosed carpal tunnel syndrome when I lost the use of my hands. I had them operated on and can type again. That is good, because speech is sometimes difficult.
I also have polymyalgia Rheumatica, which is very painful. That is diagnosed by a blood test. It is in remission after a course of prednisolone, which also stopped me leaking. Dr. says it does that sometimes. A bonus. Childbirth is not without it's adverse effects.
I have 21 items on my repeat. They all work, because I have not been in hospital for a long time. I buy vitamin B complex and vitamin E, which are fairly cheap and not POMs. Vitamin B complex cure the sores which come in the corner of my mouth, so I know they work. Vitamin E is for nerve repair. They don't heal nerves, or there wouldn't be any paraplegics, but I have noticed a difference over the past 4/5 years. I had them posted in Covid, and still do. They are in my notes.