Getting hit in the back of the head can be fatal and can cause brain swelling. You probably have a concussion. Which just means ur brain is bruised from shaking too fast and hitting the side of ur skull. U know when u have a concussion if u get tired easily, dizzy at times, odd sleep, head feels like a microwave, thinking is harder, feel a little drunk all the time (low self control and impulse control) U might have trouble speaking during a Concussion but most likely would heal out of it as long as you don’t have permanent brain damage.