WorriedinNYC,

Get off the worrying bandwagon. Second impact syndrome would not apply to you. You are too far removed from the first impact.

It sounds like you have an unstable neck. The jerks and sudden movements put a strain on your neck. Resolving and displacement and strengthening your neck will help. A NUCCA chiro or good whiplash trained PT or osteopath who understands whiplash or maybe a Physiatrist (Physical Medicine and Rehabilitation) can help. Just remember, not all medical professionals with the same training have the same skills. Finding a good one can be a challenge.