good morning sorry to hear about your illness These symptoms would strongly indicate ulcer or erosions in your stomach which needs immediate upper endoscopy Upper abdomen is the area where stomach and duodenum (upper small intestine) are placed. Burning in this region would strongly suggest increased acid production in stomach which would be hurt by the orange juice (again acidic) that you consume. Black stool indicates that you may be passing a partially digested blood in your stool and this blood may be coming from bleeding from these ulcers or erosions which can occur due to high acid production in the stomach. so you need an urgent upper endoscopy. I would also test H. Pylori bacterial infection in your stomach in this process as it commonly cause ulcers. I would also strongly suggest to avoid any pain medicines containing NSAIDs, aspirin which can again aggravate the situation So rush immediately to a gastroenterologist Hope this would answer your question Wish you speedy recovery