I think everyone is different. Are you temping?? Using both of these in conjunction will give you a much better picture, although its kind of all in hindsight. I used OPKs this month for the first time and got a BFP, but its still hard to determine if i Od on the 17(when i got the last positive) 18 or where FF put me at the 19. Not that it matters once you get pregnant. Are you charting with FF?