Flybymike's got it right. Its all about your senses giving your brain conflicting information e.g. if you are looking at instuments while in turbulence your eyes are telling you that you aren't being thrown around but the balance mechanism in your ears is telling you that you are. So keep your head out of the cockpit as much as possible and look around the horizon (good airmanship anyway).
When I first began flying gliders I thought I might get air sickness and so I did, although only minimally. Now when I fly into what you call turbulence I recognise it as thermic activity and therefore just what I want! Learn to accept it, you'll soon get used to it.
