I used to do a lot of flying (as a passenger) in and around the nether regions of Scotland in all weathers, within a short period of time I got used to the severe turbulance and rarely felt ill (unless it was self inflicted!
).
Good advice has been given so far, I would thoroughly recommend that you ensure you're thoroughly hydrated and rested before flying. Mints with a low sugar content while flying are also a good remedy, as is pure tomato juice with plenty of ice (no vodka or lea & perrins
), or just cold water in small amounts.
Believe me, you're not alone in suffering, a days sortie of recurrency training for re- hired pilots (post 9/11/01), on a large turbo prop had to be scrubbed because all of them got air sick - and they were only in the radar pattern!