What Causes Spotting Post Menstrual Cycle?

Hi my name is Nikki I'm 27 this year I started my periods at 20 of Jan and ended 5 days later they came early this mnths its usually the 28 of every mnth,wat worries me is that after my p endes I startes spotting for the next few days mAybe for a week afterward it turned into clots that came out no pain nothing umcomfy it ended Sunday all of the bleeding,wat wrong with me thank u