Women don't just use birth control pills to prevent pregnancy. I have a cousin who, when she first started having her menstrual cycle, had heavy and painful ones. She could not walk because her legs and abdomen were so painful. The doctor thought she might have endometriosis, but she didn't. The doctor then prescribed her birth control pills to control the hormonal processes that were going on in her body. After about 5 years, her cycles regulated, and her painful cycles slowly subsided. She is now off of the birth control pills.