Diarrhea..

I have really bad diarrhea and the last time I went it was super dark green like it could've been black. I've only ate chicken noodle soup and toast, I've been drinking gatorade. I've have had diarrhea about 5 days I think. With a day or two without diarrhea. I'm so confused and I might be really dehydrated. Can anyone help at all?