Ovulating early??

Amanda
So... I've kinda expected this but I think I ovulate sooner than glow says I do.. It says my fertile week is supposed to start the 28th. But kinda expecting that I might be ovulating sooner.. Hubby and I started BDing after AF... Today while wiping, I noticed some slippery CM and I took an OPK and it was pretty dark, maybe not quite positive yet but close.. We've been TTC for 8 months, kinda sticking to Glow and when they tell me to do everything... Maybe my body is just different... Anyone else ovulate sooner than glow says??