Hello,
Missed birth control pills can have lot of effects. I hope you haven't stopped your birth pills all together.
Birth control pills are hormones that prevent ovulation and therefore prevent pregnancy. When you tend to miss the pills, irregularity in cycle sets in. Its fine you missed pills now, but don't stop with your pills. Continue with taking your last missed pill, by this I mean take two pills in one day. Then continue with the normal pills. Try taking pills everyday at same time. So that you will remember taking it every day.
What you are having is withdrawal bleeding. If you continue with your pills, it should ideally stop in another two or three days. If not consult a gynecologist.
Thank you.