How old are you? Do you have bloating, loss of appetite, diarrhea/constipation, nausea/vomiting? Is the ball increases on coughing, sneezing or straining?
An abdominal hernia is a possibility, like paraumbilical hernia. This can occur due to weakness of the muscles. This becomes more prominent when one stoops or strains the abdomen wall by coughing, sneezing or carrying weight. An examination by a physician would be prudent. Treatment is usually surgical though an abdominal corset may be tried.
Please feel free for your follow up questions.