I would suspect the latter, or that you have a particularly low tolerance to, or even mild allergy of alcohol. Clearly your body is saying it doesn't like the aftereffects. Try drinking fewer quantities by interspersing non-alcoholic drinks between alcoholic. Drinking on a full stomach (of food), and drinking some water before going to bed should help too. The only proven remedy to a hangover however is time: it takes about 1 and 1/2 hours to process a single drink.