How To Treat Irregular Periods After Delivery?

Hi, may I answer your health queries right now ? Please type your query here...i am a breast feeding mother my baby is 6month .After delivery my period came in 3month but it become irregular last 2month my period has not come yet .I have already test my urine for pregnancy after 8days delayed of my due date.My LMP is 21.12.2010.the test was negative.till now my period is not coming yet.What shall I do ?