The birth control pill is meant to be taken at the same time every single day. If you miss a pill or if you don't take them at the same time, then it lessens the effectiveness of the pill, putting you at risk for pregnancy. If you have been sexually active, then you might be pregnant. Since your period is late, go buy a home pregnancy test and take it tomorrow morning with first morning urine. If you are not good about taking the birth control pill, then you need to make a doctor's appointment to talk about a better birth control option for you to try. There are many different options, such as the depo shot, implant, birth control patch, vaginal ring, and so on, that don't require you to remember daily. Though take the test and then go from there..