After a birth, even stillbirth, hormone levels can take some time to return to normal. With a normal delivery, discharge can continue up to 6 weeks or even two months. After this time, normal periods may or may not establish themselves....it is different for everyone. Breastfeeding, stress, diet, how much rest a woman gets, etc, are just some of the factors that effect the return of a normal cycle.

It is perfectly normal to be somewhat irregular for a while, but if you are concerned that you are pregnant, you should take a test, especially since you would want to have closer monitoring of future pregnancies because of your history.