I deal(t) with these problems permanently, I feel you.
It started when I wasn't even 2 years old, I frequently fainted randomly in my parents arms, but always gained consciousness within a few seconds.
It never stopped since then, I find myself unconcious at least once every 3-4 months so I gained some experience on how to deal with it before it happens. It's getting longer too, longest time-out was over 5 minutes. Doctors said it's definitely epilepsy + my very low blood pressure. Often tired even though I get my 8 hours of sleep, it's rare that I'm 100% energetic.
When I feel it starting I instantly lay down, feet up. I lose my balance, my head feels like it's about to go off, my vision turns bright-white or pitch-black until I'm out. I rarely 'catch' myself. If someone is near me I warn them that my lights are going out so they don't suffer a shock, that happened too often. Waking up & realizing the person next to you is completely pale, crying & in a worse state than you are. After waking up you feel weird for 10-15 minutes, like everything is moving inside you, hard to explain. Sometimes I wake up & feel better than before, really strange.
Every so often it all happens too fast & I fall, hit the bed or a table which results in crazy concussions, sometimes my vision was so f'd up after waking up I couldn't tell apart the medic from my friends. The 2 worst surfaces my head hit were a chemistry brick table (8th grade or so) & these smooth white bathroom tiles. Those 2 falls were bad bad, I still remember the pain in the back of my head. My biggest fear is it happening in the ocean or something, I'm swimming a lot. That's it then, no respawn, I doubt someone could get me in time.
You said you get light headed? Sounds like low blood pressure... Just test it every morning for a few weeks & see if it's that, some people go their whole lives without knowing they're suffering from hypotension. If so I recommend avoiding lemons, I find that it lowers it even more. Instead, eat a little more salt (don't overdo it, unhealthy) & drink more water than usual. Cold showers also help, it keeps the blood flowing. If you don't feel like cold showering, just shower your legs. And exercise, ideally don't do heavy deadlifts & stuff like that.
Oh & and don't stand up too fast. I sit on my bed at least 10 minutes before I get up so my body gets used to the change. It happened too often that I just instantly stood up in the morning & involuntarily went back to sleep again - good night.
Unfortunately I don't know about your post concussion syndrome, the effects on me after a concussion only lasted about 2 weeks at the absolute max & besides I haven't had a concussion in years, I learned my lesson trying to stand & wait it out during a faint. Wishing you all the best.