AF late . Fertile window changes??

Erin✨
This is my first cycle without birth control and ttc! Every time I say my period is late my fertile window moves is this accurate?? I wanna use opk this next time around if AF ever shows up that is! Took a few hpt last week all negative! Idk if i ovulated and if I did if it was the date glow says or not :( staying positive baby dust to all ladies ✨✨✨?