You are not alone! I have suffered since I was like 5. I remember throwing up on field trips, between classes, the day my dad dropped me off at college I puked all over the back of the car. Not to be gross.
My anxiety gets me nausious and that then creates another response that gets me with anticipitory anxiety if I am in a situation that I may feel that way.
Flying on an airplane is the worst for me. I have learned to control it and work thru the fear and the nausua. It isn't easy, but you can do it. You need to remember to keep breathing. You can't gag if you are breathing. Concentrate on something else besides what is going on right at that time. think about your family, your hobby, something else. I have a security blanket, I guess you could call it. I suck on Lifesavers if I start feeling that way. It seems to help, but that is just me.
I hope this helps.