You can purchase pregnancy tests from the pharmacy that can detect hcg as early as 2 days after you have conceived your child. I would buy one from a chemist or supermarket... they are just as accurate and cheaper! I do however know that hcg levels sometimes don't rise until 2 weeks after your child is conceived so do a test (if negative)  you then don't get your period retest 2 weeks later.

when i last look a test, the test said i could take it from 7days after concieving well, it was neg but i was preg, i took another test 2 days past my due date which was pos. i would get a blood, only way to get a definate answer. especially if you want one right now good luck

As far as I know most home pregnancy tests can show up from 7 days before your period is due; The doctor can do a blood test though which can show a pregnancy after 3 days.