Why Does One Have Light Bleeding During Menstruation?

Hi Dr i have a problem, After 45 Days I Got My Period (Light Bleeding),for the last 9 days iam getting light bleeding. but This Was Not Like A Normal Period.This haven't happen to me before.I even took Pregnancy test a week before and it was -ve, Now iam Confused Whether it leads to any other problem ? kindly tell me the ways to get away from this problem