Quite honestly I think you're best off not worrying.

I thought for about a year it was my brain that was sensititve.

A year and a half later, I'm 100% sure that my neck is causing most of the head sensitivity if not all of it.

You seem cognitively pretty good.

My advice:

1) Get the neck treated. I posted a free program I found that worked better than any PT plan.

2) Do some vestibular therapy exs.