I've had diarrhea for 3 days?

I'm 16 and I've been having an upset stomach and diarrhea for 3 days. I don't wanna gross anyone out! My poop comes out in little pieces and watery. What's wong with me? I've been eating normaly, rice, chicken, eggs, bread, water, mashed potatoes. I also drank pepto bysmol and it didn't really work. What can I do!? I really don't wanna go to the doctor!