Is your headset too tight? I first felt sick in a Cessy when I borrowed a pair of DCs which held my temples like a vice. (Next time I felt airsick was in my Mooney as it fish-tailed endlessly... well for several minutes in thermal bumps doing 165
).
The legendary Chuck Yeager says in his autobiography that he got airsick on his early flights but overcame it.
Ocean yachtsmen (and rowers) get over the initial sea sickness with a fantastic anti-emetic from New Zealand called Paihia Bombs available on the web at
Paihia Pharmacy
It's not a drowsy one so it might just be suitable for flying - maybe worth checking.
Good luck!