I have the same problem and i have to drive on some bad back roads, it could be your back, but i was told it was the fluid around my brain that makes it flare up bad for me. you had a head injury, no matter what it can take a long time to recover depending on the person. your neck and brain are being shook over bad roads! ever try to hold an uncovered drink while driving? the cushion may just help! it may act like a shock absorbent! good luck!

RP