To use an early pregnancy test, you should be 3-5 days after your period is overdue. If the time is too short, there is often a false negative, that is, although the test is not pregnant, but actually pregnant, because the time is too short, did not check out, the longer the time, the more accurate the test results. If you want to know whether you are pregnant or not earlier, you can go for a blood chorionic gonadotropin test 10 days after having sex during ovulation, which can tell you whether you are pregnant or not at the earliest. If you want to know more accurately whether you are pregnant or not, you need to go to the hospital for an ultrasound examination more than 10 days after your menstrual period. If a gestational sac or a primitive heartbeat is found in the uterine cavity, a more accurate diagnosis of intrauterine pregnancy can be made.