What is the feeling of a ruptured spleen like?

You may have acute. Abdominal pain, left shoulder pain. Your pulse will go up and your blood pressure will drop.
Left-side belly pain. A ruptured spleen usually (but not always) follows significant abdominal trauma. Abdominal pain, most noticible in the left upper quadrant (left-side under the rib cage) is the most common complaint. As the blood irritates the diaphragm, left shoulder pain may occur (called kerr's sign) due to referred pain. As blood loss occurs, low blood pressure and fast heart rate are seen. Get some help!