There is a possibility of pregnancy after unprotected sexual intercourse, even if you are not sure whether semen entered the vagina. Pregnancy may still occur if sperm reaches the vagina, and irregular periods can make it harder to predict fertile days or the expected date of your period. The most important step now is to take a home pregnancy test. These tests are most reliable from the first day of a missed period, or about 14 days after unprotected sex. If the test is taken too early, it may not be accurate, so repeating it after a few days can help if the first result is negative and your period has not started yet. If the intercourse happened within the last 3 to 5 days, emergency contraception may still be an option, so it is important to speak to a doctor or pharmacist as soon as possible. They can guide you on what is appropriate for you. If you remain worried or your periods continue to be irregular, it is best to consult a doctor for proper advice and future contraception planning.