It sounds like you're having a bit of vertigo, not uncommon on car or plane rides. if you are only stopping every 3-4 hrs, you probably would do better breaking up the trip a little more. Most adults should stop every 1-1/2 to 2 hrs so they can stretch their legs, preventing deep vein thrombosis(life-threatening blood clots caused by long periods of inactivity.) Get out, walk around, drink some water. That should help. Also, don't read or lot down in the car as it fools your brain--your eyes say you're sitting still, but your inner ears says you're moving, which is one cause of motion sickness or vertigo.