What could i have eaten to cause a mild bout of Diarrhea?

The dry mouth is an indication of mild dehydration which is probably due to the diarrhea. Even though you drank loads of water, you may still need more. The other symptoms sounds like you are allergic to something among what you ate. Most people with IBS have a mild allergy to milk products and cannot digest lactose. Another possibility is that a gall stone is blocking your bile duct. If you later have severe pains on your right side emanating to your back and arm, then this is likely the symptoms of passing a gall stone. One home remedy to relieving the pain and quickening the passing of a gall stone is to drink a cup of olive oil. Seriously. A half cup might do. The pain should go away in about 30 minutes after drinking the oil, but otherwise could last for days. Surgeons will advise you to have your gall bladder removed, but the procedure is very dangerous. If you have gall stones, it is safe to live with them and eliminate them with a vegetarian diet (no more milk products) or simply keeping a bottle of olive oil close at hand. Do not heat or cook with olive oil, as the heat will chemically convert good oils into bad oils.