Just go at it everyday Flashy, than you can't go wrong.
Personally, only had two, but could pin it down both times to 11 days after the end of my period.
How can you say 'before' when you don't know when will be your next ? .. like when people gave me directions (usually men) ... "and before you get to the garage ... turn right, if you have gone passed it you have missed the turning" ....
