What causes excess flatulence? (i barely drink milk or anything dairy)

Fermentation. The bacteria in your colon digest the fibers and other food types in your diet. They convert these foods into gas. (particulary foul smelling hydrogen sulphide ) try switching up your diet with different type of fiber sources and proteins lower in methionine and cysteine .May consider possible probiotics. If you are on medications then this may also be contributing your your excess gas.