This game is good and I am loving it but I get motion sickness while I play this game and it just made me vomit twice the last time I played it.
Hmm... if you tried to play on the web, I suggest you give the downloadable version a go.
The performance if much better and you may have a better experience. If it doesn't help... well, sorry.
I get motion sickness when watching other people play FPS, so I know how it feels. Good luck!