Re: psychological vomiting
I kinda know what your talking about, I've never actually made my self vomit from thinking about it but I sure get icky feeling.
I next time you start to think about it change directions and think of something else pleasant. You might try sucking on a Tums or Rolaids when the nausea starts it seems to work for me.
I would guess that your probably just working your self up worring about the act of vomitting that you actually do get sick.
Good luck and you might want to mention this to yoru Dr next time you go, couldn't hurt.