Did the car accident cause permanent brain damage or will I recover?!

I was in a car accident 3 days ago and suffered a head injury; whiplash / concussion more specifically. I hit the back of my head twice against the seat, once with my head turned, another while I was looking straight forward. I was pushed about a mile going 50MPH by a car behind me, he was having a seizure. I then drove off into a sidewalk, crashed into a pole, and stopped the car while the man having a seizure flipped over and went into the woods.
Since the accident I cannot think straight. I have trouble holding onto things (I was told this was because of the neck injury/ muscles). I am in college and when I study I find it very difficult to do so whereas before it was easy. I am very concerned that I have permanent brain damage and I hate having to function this way. I also forget a lot and am overall confused very frequently.
I was taken to the hospital via ambulance immediately at the scene as have since followed up with my doctor. While I have sustained minor injuries, I am otherwise ok.
How do I know if I have permanent brain damage or will these feelings go away soon?