Im sorry to hear about your symptoms.
You are right that you can have black stools after drinking peptobismol and the black stools can last for several days following use of peptobismol. So the black stool can still be the result of pepto however your other symptoms certainly warrant investigation. Now it is possible that you could have developed a viral gastroenteritis especially if you have diarrhea. However if there is no diarrhea then gastroenteritis is less likely to be the cause.
Another cause of these symptoms can be gastritis which can cause pain in the abdomen which can be burning in nature. It can also cause nausea, black colored stool due to bleeding from the stomach and vomiting as well. This can of your symptoms. Gastritis is basically inflammation of the lining of the stomach. This can be treated with the use of OTC prilosec which should help significantly with the symptoms.
Now if there is tenderness in the abdomen then that is a sign of an organ being involved which could be the gallbladder if the pain is in the right upper abdomen or even the pancreas. If there is abdominal tenderness then you should have it examined by visiting your doctor as soon as possible. If the pain worsens at any time then it would be wise to go to the ER.
If the black colored stool doesnt subside within the next 2 days, then it is possible that you could be bleeding from the stomach and in such a case you should get an endoscopy alongwith a stool for occult blood examination done. This would rule out gastritis and an ulcer in the stomach.
The fact that coffee upsets your stomach means gastritis is a more likely possibility here and i would suggest you consider using OTC prilosec but DO keep an eye out for the black stool and if it doesnt settle, immediately contact your doctor. If the pepto was used more than 5 days before the start of the black stool then again you should see your doctor ASAP.
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