I have been experiencing acidity (heart burn) quite often and am only 20 years old. sometimes i either vomit it out or i get a diarrhoea.. ?

Time for a GI eval.: One would consider getting a gastroenterology evaluation as to inflammatory etiology /like celiac disease ? sprue etc need further evaluation Monitor which food can cause the issue

Severe GERD: with diarrhea will raise the possibility of a Gastrinoma. See a doctor for the management of GERD. avoid smoking and keep upright during meals and 2 hours after meal.

See G.i. doc: Frequent heartburn with emesis needs to be assessed by a gastroenterologist. At your age you need to find out if you have a hiatal hernia or some other problem that requires more than acid neutralization and diet.Good luck.