What Causes Heavy Bleeding During Menstruation?

hi, ihave heavy bleeding from the last 13 days and mt bleeding started after the one week when i had emergency contraceptive pill. i had ecp on 15 january and my bleeding stated from 21 january n its continue till now initial 7 days bleeding was very light bt frm the last 5 days bleeding is heavy and having some clotting . kindly tell ma what is the reason of continue bleeding ? because its happend first time and my normal periods bleeding days are just 7 but this time its continue from the last 13 days means today is 13 day of bleeding. how will i stop that bleeding? is that harmfull for my uterus?