The chances of getting pregnant from unprotected sex on the first day of your period are extremely low, as ovulation typically occurs much later in your cycle. However, because sperm can survive for a few days, pregnancy is not entirely impossible if you have short or irregular cycles. There is no need to panic. You can certainly use a home pregnancy test kit to be sure. However, testing now is too early. For an accurate result, use the kit on the first day of your missed period, or at least 14 to 21 days after intercourse. If this happened recently (within 72 hours), you may also consult a healthcare provider about emergency contraception.