Some women have very regular cycles and some have irregular cycles. Especially, if just coming off birth control. But if your period is late or you missed it entirely, it is normal. Its absolutely normal for your period to be late, normally due to ovulating later than usual. Sometimes, you can even have a anovulatory cycle due to not ovulating that month. Which is also normal. But if its been a few months with no period, that's when it should be of concern and you should consult with your doctor. But once in a while is completely normal!