If you notice this anywhere else in addition to the cojo side, it is possible that you have developed some inner ear infection, or other physiological problem that you should get checked out. If not, then it's probably just a combination of nerves and gyrating around low-level. And despite the encouraging brilliance of the above post, if you're prone to this sort of thing, it doesn't matter much what you're in.
So, barring some medical problem, why are you getting sick? Although other physiological factors may come into play as well, motion sickness is primarily caused by conflicting messages to your brain from your eyes and inner ear. Funny enough, that's the same thing that happens when we get food poisoning. SO, back when our bodies were designed (Lu may be able to help on this), nobody thought about riding around in boats or air machines, so the software read: “If conflicting signals are received from the optical nerve and the gyro input, THROW UP. Obviously, we're being poisoned.”
Anyone can be airsick given the right combination of factors. One airborne survey operator I flew with had been sitting left seat during bird-towing work for 15 years, and probably over 10,000 hrs. He would hammer away at his keyboard, make notes and check data for hours at a time, and never look out the window. I was sure this guy had a cast-iron gut until… One day, while towing in a particularly nasty piece of rock in the Kiglapait Mountains, Labrador, he looked at me with a wide-eyed stare and said, "I can't believe it, I'm going to... BLAEHHH...". Nice. First time in 15 years.
Bottom line - in addition to some of the good advice above, try to provide the brain with concurring signals from the eye and inner ear. Look out the front. Don't read. Don't put your head in your lap. Don't lie down in the back (R22 notwithstanding). As previously stated by others, it's unlikely you'll be sick when you're doing the flying yourself.
I'm sure you'll get through it, have a great career.