Pregnancy can be detected as early as 10 days, you can see your doctor for a blood chorionic gonadotropin test 10 days after sex, if the value is greater than 25mIU/mL, consider the possibility of pregnancy, or basically can confirm pregnancy. You can also wait for a few days, and if your period is more than 3 days overdue, you can buy an early pregnancy test and use your morning urine to check if you are pregnant. If you want to be more accurate, you can wait more than 10 days after your period, that is, more than 40 days after your pregnancy, and see your doctor for an ultrasound. If you can find a gestational sac in the uterus, you can be sure that you are normally pregnant. A blood chorionic gonadotropin test can be the earliest way to know if you are pregnant, and an ultrasound can be the most accurate way to know if you are normally pregnant.