What Causes Vaginal Bleeding Post Menstrual Cycle?

Hi i am a 27 year old woman I gave birth to my third child on march 1 2010 and also had a tubal.Ever since then i have gotten my period on time but its been heavy.This month i stated on the seventh and ended on the twelveth but this period was lighter than the others. Then right after i started having a light brown mucus discharge i have had this after every period since my tubal.Well last night when i wiped it was a lot more brown discharge and this morning it was some more blood.Now its brown again not really mucus just brown and only when i wipe. Please help