Most fertile time is around 14 days into cycle (assume 28 day cycle) then period would be due at 28 days and to get a true result it can take around a week to be sure of a true result.
some tests claim to be able to test for very small amounts of hormone up to 5 days before a period is due, but they only have around a 50% success rate.
Are you trying for a baby too? I have been for 6 weeks but feels like a life time!! No such luck yet and to make it worse I don't even think I'm ovulating so its probably impossible at the moment. If you want to keep obsessively testing like I do you can buy the cheap tests from the �shop! I got 3 for �1 and I do one every week! Happy trying and hope you get the result.