Period from sep 15-20th. started taking birth contol pills. took them wrong. took last pill the 21st. for 2 days have had pink discharge what is it?

Not sure exactly..: .. how you "took them wrong" but almost any variation from the prescribed directions for birth control pills can result in a small amount of bleeding or spotting from the vagina. The lining of the uterus is very sensitive to hormones in your system; exposing this lining to unexpected hormones can cause this small amount of bleeding. If it has stopped, nothing to worry about or do. Good wishes:)