Glow vs. Other fertility apps

I have been using glow and another fertility app and my periods are never the same from month to month.. I just got my period Oct 6-9 and I took a ovulation test the 13th and it had 2 lines meaning I was ovulating but glow app still says my fertility window doesn't start till next week.. but the other app shows this week is my fertile week I'm just confused and trying to conceive my second child!! Thanks any opinions will be helpful!