What Are The Reasons For Black Stool Passing Black Stool Since Souple Of Days?

Passing black stool since souple of days? - what are the reasons for black stool

In the last two days I will have a black stool. I have serious heartburn as well, then what is the reason why black stools. I also have a cold sweat when I feel lethargic or fatigued. Please help me, what are these. TKS