I had a patient come in one day because she had missed her period. I gave her a pregnancy test, and yes, she was pregnant. She couldn't believe it, because she was faithfully taking the Pill. In my experience, this happens because the Pill isn't being taken correctly, so I asked her what she had been doing. She admitted she didn't like the Pill--it was making her gain weight--but she was still taking it every day, either in the morning or at night, and when she forgot, which was often, she doubled up. That meant if she forgot one day, she was possibly taking two pills the next night and then another the following morning, so her hormone levels were fluctuating wildly--and that's not going to protect you against pregnancy. What's more, when you repeatedly take a large amount of hormones at once, it can put you at risk for dangerous blood clots. You need to take the Pill exactly as prescribed, at the same time of day every day.