Hello, and I hope I can help you today. Loestrin 24 is an effective birth control pill, but it is very low dose. Sometimes even a small deviation in your schedule of when you take your pill can make you have breakthrough bleeding in between your cycles, especially if your period is normally very light or doesn t come at all. However, the pill is 99.5 percent effective, but that means 1 in 200 women per year get pregnant on the pill. So I would wait until the end of your pack when your period should start and do a pregnancy test. Your test will become positive a minimum of 2-3 weeks from conception, so it may be too early to test. People who accidentally get pregnant on the pill had been extensively studied, and the pill has not been shown to cause birth defects. So you do not need to stop the pill if you are worried you could be pregnant. It is common for women who are worried about pregnancy to have symptoms they think are due to pregnancy, especially if they have not experienced pregnancy before. So try not to worry until you do the test. I hope I was able to answer your question and that my advice was helpful. Best wishes, Dr. Brown