What this black stool means is that your are bleeding from the stomach on up. The blood comes in contact with the acid in you stomach, it turns black. Free blood, even if "cooked" by the acid in your stomach, will cause irritation in your intestines, thus cramps. The diarrea y part of the profile. Minimum blood loss, 50cc daily. Medical evaluation necessary.
Probable causes:
- Gastritis with stomache ulcers
- H pylori
- Esophagial bleeding
Welcome to the gastroenterology community! I doubt it is a blockage. Unless you are taking any medications now, the black color could indicate blood in the upper part of your intestines. You need to be checked out by a doctor ASAP.
Possibly a blockage working its way through.