Hi. Please Answer. Is ECP/morning After Pill Can Cause An

Hi. Please answer. Is ECP/morning after pill can cause an advance menstruation? What happened is like this, January 4 take an ECP. The expected period is January 12-15. But on January 9, theres a brown and a little like chocolate. But like a melted chocolate until the afternoon of January 10. And then afternoon, started of a medium amount of blood. With the mild cramps and the feeling of the start of the menstruation. Is it possible that it is real menstruation? Or withdrawal bleeding? Or implantation? Please reply. Thankyou so much.