Hi there. Welcome. Well, not sure. Birth control pills can fail on rare occasions especially if someone isn't taking them correctly (or misses a pill, takes two the next day, that kind of thing). Typically, birth control pills regulate when a 'period' comes. So, it is odd to skip your period while on birth control. But again, if you had any days that you took them in a different way last month, that too can throw things off.