Given your history, it is not probably that you ruptured your spleen. The spleen is in the left upper portion of the abdomen, it is size of your fist and has the consistency of a grape. Often, trauma to that area causes a fracture of a rib, and the rib then can cut or lacerate the spleen. The vast moajority of injured spleen are lacerated and do not rupture. Most bleeding spleens stop without surgery. The pain most likely is that from a broken rib or ribs. Broken ribs are often detected by chest x-ray, and even then some people will have broken ribs with a normal chest x-ray.
Since there was no "blow" or trauma, this complaint likely represents a strained muscle.
This information is not a replacement for consultation with your personal physician.