I think im pregnant. when can i take a test? had sex a week ago and period was due yesterday nothing still. how many days do i wait? on pill

If no withdraw bleed: A urine pregnancy test gives a very reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a withdrawal period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal withdrawal period, then she is not pregnant and a test is not needed.