a week late

Hi so i had my baby on August 24 i was bleeding for two whole months non stop while breastfeeding they told me i had cyst and the doctor put me on birth control and told me they should go away so the bleeding stopped and i got my period every month just last month i stop taking the pill and now im a week late im still breastfeeding ive taken a pregnancy test and im not pregnant can it be that i haven't gotten my period dude to breastfeeding?