I am an instructor with 2500hrs and still on occasions still feel sick. I can't read when travelling as a passenger, feel sick on x-channel ferries. I find I build up a resistance to it, but if for any reason don't fly for a bit, holiday/sickness etc I become more susceptable to it.
I have never had a problem on a commercial jet, but lighter aircraft, being less stable and spending more time bumping around in all the crap can sometimes be a problem. For obvious reasons I have avoided aeros......
Its rubbish to say its psychsomatic. Its caused by the mis-match of information that your brain receives. Your balance says 'we're all over the place', your eyes say, 'I'm sitting in a seat', your stomach says, 'Ralph & Huey'! You train your body to get used to it, then try and fly a simulator without feeling sick!
Must try the ginger tho'.