My son had similar symptoms and gaze stabilization exercises were critical in his recovery. No way could he have handled shaking his head back and forth at the beginning! Sounds like you are going too fast. Start by sitting in a chair and have someone turn your head for you to take your neck out of the equation. Have them turn your head left to right, left to right while you stare at an object. That's it. Twice to start. Do that a couple of times a day until you can do it yourself. Then you have to do the same for up and down. You have to build it up slowly. It sounds crazy, but I swear it works!