fertile window and ovulation sign- newbie!

Je
My period ended almost a week ago and so far the closest I've had to a positive opk was during my period, right at the end, though even that wasn't fully positive. Now I'm apparently in my fertile window according to glow (I know that may be wrong since I just started tracking) and my opks are still negative, very negative, and I checked my cervix just now for the first time and I'm pretty sure it's low and closed.
My ovulation day is supposed to be Saturday (currently Tuesday) so my question is with negative opks and possibly low and closed cervix, can this all change in the next few days or does that usually not happen that quickly? Or is it more likely that my suggested ovulation day is totally wrong? Thanks!! :)