How long untill u know if your pregnant after sex ?

2 weeks: A woman who needs to know if she is pregnant can use an over-the-counter urine pregnancy test (they are very accurate) from the drugstore, 2 weeks after having sex. If it is negative, and her period still doesn't come, she can repeat a test 1-2 weeks later.

Within 10 to 14 days: If you had genito-sexual intercourse with a fertile man about the time of your ovulation and if fertilization did occur, a blood betaHCG pregnancy test will usually be positive 10 days later. Most urine pregnancy tests will be positive about 14 days after fertilization.