Concussions are a scary thing to go through. For some people, especially young people it can trigger an episode of acute anxiety and stress. It sounds like you've got yourself very scared about what could be going on in your head physically which is very easy to do if you start reading around on the internet. The personality changes, the fogginess and slowness are all common symptoms of ANXIETY and so not necessarily evidence that you are suffering from PCS (although PCS just means you are ill after a concussion so it could be called that).

My advice is to STOP reading on the net about what might be wrong with you and to take it very easy for a while. Do things that you enjoy, be kind to yourself and find ways to calmly distract yourself from things which trigger your anxiety. Getting some medication for the anxiety may help. Some therapy may also be beneficial especially if you have suffered anxiety or depression in the past.

I suffered a relatively mild concussion from which I thought I had recovered a few days later. I've been struggling with depersonalisation, derealisation, anxiety and depression for the past 8 months since but am about a million times better than I was 7 months ago. But when I took a look at my life pre the accident I realised that I had been dealing with all these things already. The concussion just seemed to tip me over and bring everything crashing down so I had to rebuild my life.

Wish you all the best. I'm certain you will be back to yourself. In fact you will probably be happier once you get through this. Just give it some time and don't for a minute think that you have brain damage cos that will suck you straight back into panic land!