If you have intercourse 3 days before your period and your period comes on time, you generally won’t get pregnant. Women who have regular menstrual periods, the day of ovulation is usually 14 days before the next menstrual period, and 5 days before and 4 days after the day of ovulation is the ovulation period, that is, easy to get pregnant, usually outside of this time intercourse, the chances of pregnancy will be greatly reduced. So having intercourse 3 days before menstruation itself has a lower chance of pregnancy, and if your period comes on time afterward, you’re usually not pregnant. In addition to seeing if your period comes on time, you should also pay attention to how long your period lasts and whether the amount of menstruation is the same as usual; if there is no change, it means that you are having your period and you are not pregnant. If the period is different from normal, it may be abnormal uterine bleeding, and the date of ovulation may have changed, and further tests are needed to determine if you are pregnant.