Just got off birth control and have a late period and really bad cramping, but 2 negative pregnancy tests what does this mean?

Hormones readjusting: Most birth control works by providing hormones that cause the body to act like it is pregnant. It is these hormonal changes that cause the body not to release an egg to be fertilized, thereby preventing pregnancy. It is not at all unusual for it to take the body a few months to adjust to the hormonal changes. Don't be concerned if it takes a while for your body to readjust.