Hello, my name is Dr.Dorina Gurabardhi. I understand your concern. 
Nausea and 
vomiting are not diseases, but they are symptoms of many conditions such as:
-Medication-induced vomiting
-Emotional stress (such as fear)
-
Gallbladder disease
-Food poisoning
-Infections (such as the "stomach flu")
-Overeating
-A reaction to certain smells or odors
-Ulcers
To diagnose are necessary some examinations such as 
blood test.
Some advices that I can give to you are:
-Drink gradually larger amounts of clear liquids
-Avoiding solid food until the vomiting episode has passed
-If you are also vomiting an oral rehydrating solution such as 
Pedialyte should be used to prevent and treat 
dehydration.
Hope my answer was helpful, if you have any other questions I'll be glad to help, thanks!