The description of your symptoms that a vomiting
happens after meal, though inconsistent, points out that it has to be evaluated in detail. If you have not an abdominal pain
or any black or blood stained stools , well and good. how long is it before you start vomiting after a meal also counts as it can give us an idea about the site of abnormality. The investigations you might need are these. Routines and stool for occult blood, barium meal
Upper gi endoscopy
. You have to get yourself evaluated. Eliminating some attention requiring pathologies, we can always search for other rarer causes. As the first step do see if you have any problem concerning the intestines.