That ammount of water is really bad for you. Also, try spreading out your meals to about every three or so hours instead. You don't want to overload your digestive system too much. You're eating a good veriety of foods though.
Losing water happens but not at that rate. Your stomach can really only absorb 500ml or so an hour. Drinking 15 pints a day seriously depletes your electrolytes and is pretty damn dangerous!
As for your sweat. Imagine getting a skooshy bottle that holds a pint of water. think how wet you could get spraying yourself with that fine mist. thats what sweating is like. even if you drip a lot you wont lose overly much sweat as your body has to draw it from the blood and tissues to sweat it.