I had exactly the same thing. My brother did too, without having PCS. It started to go away when I started to relax, I think it's anxiety related. It's starting to go away completely now, and I'm 2 and a half months post injury. You have to understand that it's only temporary, it's incredibly unpleasant but it's only temporary. You need to be very kind to yourself. Try and find things that make you feel better and do a bit of that. For me it was talking.
Positivity is hard but important at this point. It's a simple matter of focussing on good thoughts and not letting the bad ones in. I'm having psychotherapy and it really helps.
All the best to you, you'll be ok!!!!