Hi there...I can understand your concern. 12 days is very late. Now there's no medication that can prevent pregnancy. If you have had you menstrual bleeding after the day of intercourse, then it's very unlikely that you will be pregnant. Now can take a urine pregnancy test and check for pregnancy. If you miss your next menstrual cycle or urine pregnancy test is positive, kindly consult a obstetrician. They will councel about further options.