What Causes A Vaginal Discharge With Clotting Instead Of A Period?

dear doc well i didnt get my period for almost 3 sometimes 6 months then i got pregnant and i lost her at 3months but then it took me 3 years to get pregnant again i had my son april 5th 2010 and i was bleeding till 27th of april so im waiting for my period but now ive been getting for the past 2 days some brown discharge with some brown blood clots but i have no pains or nothing i took the preg test but neg can u help me what does it mean