I'm having watery stools which are black in color, i've taking pepto bismul and still no relief. what can i do to relieve this diarrhea?

Be seen: The black color is most likely due to the bismuth in the pepto-bismol, but you should be seen to get some diarrhea medication and possible testing.

Nature might help: Apples, bananas, breads & rice have some constipating qualities when consumed. They are a natural way to add bulk/slow simple diarrhea. Imodium is an OTC med that is well tolerated. Avoid juices that loosen stools=apple,prune,grape, etc. In time you may need to be seen to make sure it is not a real problem.