Hi i will try my best to answer your query
Black color stools may be due to iron content in your haemoglobin
capsule, so no need to worry about that.
White discharge can be physiological also, but if it is thick, foul smelling and associated with itching then it could be some infection causing cervicitis
, if so consult a gynecologist and get per vaginal and per speculum examination.
Hope my answer will help you.
take care, bye