Hello, and I hope I can help you today. Typically, women are advised to start birth control pills within seven days of their last menstrual period because it is unlikely that she would ve already ovulated at that time. If you start the pill later in your cycle, the process initiates ovulation may have already begun and your body may produce an egg that is capable of being fertilized that cycle. However, even if you ovulated right when you started to take the pill, it is unlikely that the egg would still be viable to be fertilized after seven days. Therefore, waiting seven days before having unprotected intercourse most likely was enough time to ensure that you would not become pregnant. Modern pregnancy tests will become positive within 10 days to two weeks after conception, so if you do not have a menstrual period at the end of your pill pack, you should perform a urine pregnancy test to be safe. However, if you start your pill later than one week after the start of your period, you may not actually bleed the first month during the pill free week. I hope that I was able to adequately answer your question today, and that this information was reassuring. Best wishes, Dr. Brown