There are several possible reasons for not having a period after taking the pill. First, after taking the pill, although the contraceptive effect of the pill is very good, but due to individual differences, some people should have the possibility of pregnancy even though they took the pill on time and in the right amount, because the contraceptive mechanism of the pill is to inhibit ovulation, once this effect is not achieved, there is a possibility of pregnancy, so if you do not have a period, it is recommended to use the morning urine to do the early pregnancy test first to rule out the possibility of pregnancy. Therefore, if you do not have a period, it is recommended to use the morning urine test to rule out the possibility of pregnancy. Secondly, the most common side effect of oral contraceptive pills is that they can cause menstrual disorders, which may also be caused by the pill, because the pill is a combination of estrogen and progestin, and after taking it, it may cause delayed or early menstruation, or changes in menstrual volume.