I breastfeed my 17 month old at nights now and i still have not had a period since conceiving my son, how come?

Breast feeding ...: suppresses ovulation. In some parts of the world this is the only form of family planning and the only way Moms can space their children apart. You may be delivering the bulk of his daily calories by breast feeding at night. Does he sleep in your bed and feed freely? If so, you may be sleeping through most feedings. I would bet if you limit his feedings to once a day, your period will return