Fertility and OPKs

My cycle is due 6/23 and I've had light spotting one day this past week. The Glo apps say that today should be my ovulation day. Just to be certain I took an opk this morning. My results were "low fertility", very frustrating. I had bariatric surgery and have lost weight and my cycles are finally regular again. I was very hopeful. Anyone else have a similar experience? Any suggestions?