What Could Cause Vaginal Bleeding After Taking An Emergency Contraceptive Pill?

Good day I m a 21 year old female. I need help, I was my periods on the 2nd to 4rth of July 2022, after that I ve been having sleeping with my partner not using protection but I took emergency pill. Today I just started bleeding and I don t know what the cause is and I honestly think it s not menstruation because there are no period pain