The strange thing about your experience is that it is tryptophan that can make you drowsy.  I don't know if anyone has ever reported a case like yours.  One possibility is that you are very low in tryptophan, unlike many Westerners.  You don't need to take gelatin as a supplement, depending upon your diet.  I take tiny amounts of some supplements, just trying to make sure that I have enough of the really important ones that I may not be obtaining enough of, so I'd suggest you only take very small amounts - perhaps 1/16 or 1/32 of a teaspoon each day, in the middle of a meal.