Thanks for your query and concern. I think this could be some unusual event. This is normal in women at times. But this can also be an indication of sexually transmitted diseases or infections. Thyroid related issues also can cause similar problems. Irregular schedules of pills are another reason for this. It is better to take a pregnancy test as soon as possible and consult your doctor for further information. If you are pregnant now, bleeding should be given utmost attention. Good luck.