Unprotected sex during the fertile days of your cycle can cause pregnancy. The fertile days are they days around ovulation (2 days before and after ovulation), which usually occurs about 14 days before the next period is due. If you don’t get the expected period and lack menstruation, you could be pregnant. Then you can take a home pregnancy test to confirm or exclude pregnancy. A pregnancy test is valid up to 5 days before an expected period is due. You must wait until that time to be sure that the test is valid. Always confirm a positive home pregnancy test with a visit to the gynecologist's office for a blood test and ultrasound confirmation of an embryo.