What Causes Black Discharge During Menstruation?

Hello There.. I got my menses on sat morning 23rd april 2010, on the 1st day i had just a black discharge and past 2 days its just not the normal flow, its very less.. what can be done or what is the problem, is this normal.I have been married for the past 3 months and dont plan to hv a kid soon.



My height is 5.7 n weight 68kgs.