air sickness is very common. The worst thing you can do is to not eat.
Eat a sensible meal beforehand as having an empty stomach actually makes you feel worse.
My favourite flying breakfast is Granola, greek yoghurt and fruit. A nice mix of carbs ,protein and some fruit sugars.
As you take over more and more of the flying you don't have the opportunity to think about feeling sick! Your mind is otherwise engaged, just in the same way drivers don't get carsick.
Keep the temperature on the cool side as well. use the cabin vents and seeing as they are on the instructor's side ; don't be shy in asking them to dial the heat down!
Good luck with the flying. If you do a google search on my username you can get to my blog and Youtube videos, I've found other people's diaries of their experiences incredibly valuable in this journey.