I had this brain sensitivity problem really bad. Others in the past have had it too. Based off of me reading about 5-10 people having it, it appears to go away in time as brain functionality increases.

It's not far fetched to believe a brain gets "sensitive" to impacts post-concussion. I don't want to scare you, but second-impact syndrome is very real. You're well out of the stages of the severe reaction IMO, but it's rational to think that your brain is still able to be irritated by non-concussive movements/impacts.

I do suggest a nutrient regimen (diet and supplements) to speed up healing.

Over time, you should find that your ability to tolerate movements improves. Yes, the setbacks/symptom flare ups suck, but your prospects are good.

The neck injury theory is something to consider too. That can cause all of the same symptoms. Neck injuries are no joke and need to be taken seriously.

You could have one or the other (neck or brain) OR both going on.