Hi and thanks for using the forum.
You said that you missed a pill, but did you "double up" the next day or take the missed pill when you remembered? The pill is an effective form of birth control when it is taken as directed (the same time every day). So it is possible, if you are sexually active and did not use another form of birth control, that you could be pregnant. Also possible is that you are having breakthrough bleeding from missing your pill. If you are worried that you are pregnant, you can take a home pregnancy test if you miss your next period (there are some tests that are accurate up to 5 days before your missed period). Also, remember there is emergency contraception available (you need to take it within 72 hours of the sexual encounter I believe) for situations in which you forget your pill or other contraception fails (such as a condom breaking). Good luck.