Thank you for the query.
Your symptoms seems to indicate peptic ulcers which do bleed from time to time (causing black stools). If your pain appears after a meal, nausea or vomiting
appears, ulcers are possible. You should also have ruled out gallstones and pancreas
disease. Especially if the pain radiates to the back.
I suggest you to visit your doctor, have physical examination, blood tests, liver tests, amylase
, and upper GI endoscopy
Hope this will help.