I got a positive opk for the first time today. Does that mean I'm ovualting today or how does it work exactly? (First time using) glow says my fertile window started the 11th and today is my most fertile day/ovualting, but other apps say I'm just a few days in my fertile window and ovulation day isn't for a few days. My bbt yesterday was 97.7 today it's 98.1 also I've been cramping today. But again today was my first positive opk so I'm a little confused.