I have replied with my thoughts when you asked this previously, hope it helps.
There are many things, but you need to see a Gastroenterologist for an evalaution. In the meantime, make sure you stay well hydrated with water, Gatorade and orange juice. Eat yogurt enriched with probiotics, with diarrhea you have probably lost all of your good bacteria. It may be a parasite, so the sooner you seek help the better.