violent vomiting

I vomit violently for no reason.  It happens once or twice per month.  Doctor does not no why?  I have had upper GI and colon exam.  My symptoms include a tickle in my throat that makes me cough, saliva glands are constantly overacting causing me to swallow way more saliva than would be normal.  My lungs hurt in the morning and I have a shortness of breath when I bend over.  I,m not overweight.  This vomiting is violent!  Every 15 minutes for 12 hours or more and my stomach is usually empty when it occurs.  I never smoked and drink very little.  Alcohol seems to be a trigger for the vomiting?  Please help.