ovulating or not?

I use opks to track ovulation. I get a positive 15 days before my period, cramps, cm change etc but this month I never got any of that but cramps in my pelvic area which were really uncomfortable. My cm was creamy most of the month and my cycle was 40 days instead of my usual 31-35 days. Is it possible I ovulate and skip certain months or am I failing to ovulate every month?