Hi there.. black stools means that there is bleeding in your stomach(gastric ulcer) or small intestine which by the time reaches rectum would have turned black.. even iron tablets cause black stools but since you haven't mentioned I assume you not taking.. abdominal pain, nausea,vomiting, bloating of abdomen, feeling full, al these are symptoms of gastriti or gastric ulcer.. Cause of it is stress, not having food on time, skipping meals, spicy foods, fried and canned foods, alcohol, smoking, tobacco chewing, tea,coffee, not sleeping on time. Al of these increase acid production in stomach and disruption of protective mucous layer in stomach and thus they cause inflammation of stomach.. Treatment includes lifestyle changes, sleep and eat on time, avoid stress, avoid spicy and sour foods, avoid smoking alcohol, have bland food, have cold milk, have frequent sips of cold water.. please get endoscopy done once and consult gastroenterologist for further management..