Sorry to hear of your struggles, and can relate with a lot of your symptoms. I had a head injury almost 2.5 years ago and am still recovering. Like you, I have symptoms like bouts of dizziness, head pressure, sound sensitivity, altered vision, hot flashes at night, headaches (migraines early on) and extreme fatigue. I have noticed patterns over this time that helped me to develop some theories that I am testing out.
After 2 years I came to I wonder if my injury was maybe 80% neck and only 20% brain injury. I do not have problems with memory or executive decision making or things like that. I am no doctor, but have read a lot and wonder if this is my case:
The uppermost vertebrae in the neck are donut-shaped, and the brain stem actually goes down inside them. If these bones are even a little out of place, it pinches the brain stem. My cat scans showed up normal too, but usually they are not looking for this sort of thing at the hospital. Someone correct me if I am wrong, but the functions of the brain stem have to do with things like balance, sleep, seeing, hearing, migraines, etc. So, if the brain stem has pressure on it, it has a harder time with all these things, resulting in fatigue.
I went to a very good upper cervical chiropractor (who you go to makes all the difference - in my case it had to be an upper cervical specialist). He took x-rays that showed a misalignment of my atlas and C-2, the topmost vertebrae. He laid me on the adjusting table, and as he adjusted it, I could literally feel liquid draining down from my head, relieving the head pressure! That was wonderful, and a few days I felt a LOT better, with less symptoms.
The problem then was that anytime I got a little jolt of some kind, the bones would go out of place again. I mean like throwing a rock, or clapping my hands too hard. The vertebrae are held in place by tendons and muscles. These get loosened in the initial impact, and can take a long time to tighten again. So, the vertabrae would go out again, and all of my symptoms would come back. Then I would get another adjustment and feel good again. This cycle went on for months, gradually my atlas started to stay in place. Then the C2 started staying put. Pretty soon I was just dealing with muscular knots and tightness. I think that a good physical therapist would have been good for me, but my chiropractor kind of played that role, I guess.
After seeing this pattern of "neck in - feel great", "neck out - feel terrible", I decided to find exercises that would strengthen my upper neck to keep it in place. Swimming was the best for me (I have a post about this), so I pursued that for a month this summer, and had great results. By the end of this past summer, I was almost normal. No more plugging ear, no more migraines, a lot less head pressure, better sleeping, a lot less dizzyness, and the best was that I could take a few little jolts and not be bothered too much.
Then fall came, and it got too cold to swim. I went downhill again, and was susceptible to any little irritation of the neck. So, I went to the local YMCA and began swimming again, and started to feel really good again. In the last month, I have had multiple days in a row of feeling perfectly normal. Not just feeling OK, but feeling really good - lots of energy and I could somehow see beauty and joy in things again.
Today is a different story, as I bumped my head really hard the other day, and actually got a lump which broke the skin from the impact. So, I am back to chills, nausea, and dizzyness, and major fatigue. I saw the chiropractor today, and sure enough, I had whacked C2 out a little. The interesting thing was that when my head got hit so hard the other day, I had no ill effects till about 24 hours later, when my neck started to get cranky from it.
So, my theory is that if I get my neck strong enough, that I should be able to return to a normal active life of work and raising my family. I have not proven this yet, but have had some hopeful initial results. I hope to let you know in a few months how it is going. It is inconvenient for me to spend time in exercise, but I am willing to do it if it means that I can lead an otherwise normal life. I also recommend daily magnesium and B complex - they help me a lot. Avoid MSG.
Sorry to ramble on here, but hopefully it will be useful information for you. There seems to be no shortcut to healing, it is a long road with lots of ups and downs. I was constantly dizzy for a year and a half, and suddenly it cleared up. I think of it as a tide coming in which gradually rises, but goes in and out a lot. Progress in not measured in days and weeks, but months and years with PCS. I do not know that this is a success story, but might spark some hope for you.