I crashed skiing back in march, definitely had a whiplash concussion. I am not sure how badly I injured my neck during the crash. Over time, I got so depressed with the concussion that my entire posture changed, I was super hunched over and prone all the time. This causes your neck to have to use different muscles to hold the head up, mainly the oscipitals in the back of your neck.

What I found was that this pain/stress in your oscipitals is connected to muscles that run along the sides of your head and thus can create pretty bad headaches and eye strain. My solution had several parts. Change my posture, hold your head up and tuck your chin slightly. I also bought a special pillow that helps create the curve that your neck is supposed to have. Finally, I saw a PT who helped me with some neck exercises to strengthen the muscles that should be holding your head up. I lay down on my back and raise my head up and hold for 10 seconds, repeat 5 times or so. You can hold longer as you get stronger.

Anyway, I found this to help a lot!