What Causes Black Stool, Dizziness, Bone Ache With Burping?

My mom was complaining of black tar-like stool today. She left work because she also felt dizzy and her "bones ached". She said it felt as if she had the flu, but she had a flu-shot. She was also burping like she was going to throw up, but did not. She has been putting off a hip replacement, so I know she takes pain medicine to help deal with the pain. The only thing I've ready right now is about bleeding ulcers as a result of taking pain medicine. I was worried it might be something serious that needs immediate medical attention.