Using soap as a "lube" cause that would make it hurt when you ejaculate or urinate. Mabye an infection also but if its the soap thing it shouldn't be an infection.
Could be anything - if it is up in your stomach area, it is probably bad food. If it is in your intestinal area it is gas or digestive complications. But -- if it is a sharp pain that hurts really...
There are litterally thousands of possible causes. these could be being overweight and so putting added pressure in the knee, cartilidge sprain/damage, ligament sprain/fracture and lots lots more my...