This is more than just being nervous it's quite a serious case of anxiety/panic attack. You need to get a referral to a psychologist or psychiatrist for counselling & possibly try hypnotherapy. Another suggestion which I don't know much about but which ihope another user will tell you about is cbt (cognitive behaviour therapy) which helps many people.

You should also look on-line & locally for anxiety/panic attack support groups, there you will find people who while their symptoms may be different will know what you are suffering & be able to share their advice & what has worked for them with you.

I used to vomit before going out through stress/fear even going to a freinds for dinner would case it, but it must be awful to have it happen publically. In my case I just kept on "fighting" my fear, it's still there but at least I don't vomit nowadays.

Good luck.