Why am i throwing up? i am not pregnant or bulimic, but after every meal i throw up a little and i can't seem to figure out what is the cause of this

Brainstem: Vomiting and nausea are due to activity of a center in the brainstem. I have seen this is many patients over the past thirty years and according to this question being repeatedly raised, it is more common. By far and away commonest cause is diet, particularly the sugar and sweeteners. It causes vitamin b1 deficiency and that makes the vomiting center irritable.