I've had some problems with motion sickness during my training too. Climbing/descending turns and turbulence often made me feel sick. Make sure you've eaten, bring water, make sure that you have enough time before flying to do all your checks as that will usually calm you down.
One of my instructors told me that he used to have big problems with motion sickness during his PPL-training he even threw up a couple of times but now he can sit in the right hand seat all day long, so exposure really does the trick fine!