AF showed up.....

So I just got off the Mirena on 8/11 and my Dr gave me the go ahead to start trying immediately. I wasn't sure how long my cycles were so I took OPKs and measured my CM. I never did get a positive ovulation result. But there was one day where I felt like I was ovulating based on my CM. Well turns out that I have a 40 day cycle. Started on 08/14 and now today.... I'm pretty bummed I wasted all that money on OPKs. On to next month....I feel like I ovulated way earlier than Glow is predicting. Does anyone else experience that due to long cycles?