I've been using glow for a year before I'd even started ttc to track my ovulation after 4 months of actually bd I decided to purchase a clear blue advanced fertility monitor, I'm so glad I did because it actually showed me ovulation 2 weeks later than glow predicted.. so glad I made the purchase as I'd been bd for nothing before. Wish me luck.. just thought I'd pass the info on as I know how how it is to wait