Completely normal. Your body is experiencing chemical w/drawl due to the sudden abscence of hormone. It presents itself much like a period. As the poster above me has already stated, its nothing more than breakthrough bleeding. It doesnt require a dr. visit or a trip to the e.r. The bleeding should subside after 3 - 7 days. You also threw off your cycle so you may have another period soon.
This is totally NORMAL. It's called Breakthrough Bleeding. It happens whenever you are on birth control pills and you discontinue using them in the middle of the pack. It happened to me when I stopped taking my birth control pills as well. If you read the instructions that came with your birth control it should tell you more about it, but there is definetly nothing to worry about. Hope I've helped you!!