Fertile window accuracy

Hey everyone, no negativity meant here. I just wanted to share my experience here on glow as far as the predicted fertile window goes. I've logged my periods every month since June 2014 and my periods are very regular (average 29 day cycles)... My husband and I have been ttc for 5 months and been going by glows predicted fertile week (BD almost every day of it)... I finally started using Opks and found out that I am fertile two days after my predicted fertile week (nothing stuck yet but fingers crossed for the near future). 
I hope this makes you think twice about only trusting glows prediction. This app is GREAT and I don't mean to give any negativity, I just want to help you all if you are only relying on the app. I know everyone is different so it obviously can in fact be accurate for some people, but sometimes it's good to try out other sources/options. 
Baby dust and lots of luck to all of you!!✨✨✨