What Causes Prolonged Period Bleeding Inspite Of Having Ortho Tri-cyclen?

I ve recently started taking ortho tricyclen lo. I m three weeks into my first pack. I started the pill the day my period started. My periods usually last 3 or 4 days. This month it lasted almost two weeks and a week after my period ended I am still seeing a significant amount of brown discharge. This is not anything I ve experienced before.