How do I cope with feeling nauseous?
Feeling sick as a symptom of anxiety is very similar in many respects to having a panic attack. In the long term the best way to address this is by unlearning the association between being sick and fear. This can be done but the means to do it requires a different approach from any coping strategy that you might use when you find yourself in the grip of your anxiey.
Details of the long term approach can be found in the general approach to overcoming anxiety - the Feelgood Way.
As a coping strategy, before learning to retrain this reaction so it no longer provokes increased anxiety, if it were me, I would try to remain as calm as possible and take myself off somewhere, such as the toilets, where I could calm myself down and where it wouldn't really matter if I were to throw up.
The way it works goes like this...
Whenever you become afraid of any symptom, go somewhere that it doesn't matter and calm yourself by focusing on something else.
Try not to monitor the symptom to check whether it's getting worse because that's exactly what WILL happen if you focus on it.