If your period is already late when you've taken the test, chances are it's accurate. The hormones show up as few as 4 - 5 days after conception, so the test should have shown positive if you were. Read the pamphlet in the test package. It will tell you how many days after conception it can detect a pregnancy.
-------------------- Formerly HanSolo. IBS, OCD, Bipolar, PTSD times 3.