Constant Severe pain and tender mass under right rib, pain on eating, lower tummy pain, nausea, blood in stool and constipation. Causes?

RUQ mass. If you have mass need to have some form of imaging study to identify the source of the mass, the mass itself could be the reason for pain. Blood in stool may be from the constipation itself, the reason for constipation needs a detailed history and exam. It could be irritable bowel, inflammatory bowel disease or mass in the GI tract, these are possibilities but have yourself checked out.