Does no cm mean no ovulation?

This is weird so every time we don’t have sex during ovulation week for some reason (weird schedules etc.) I have perfect ewcm that week! But the other months where we do have sex that week I have like no mucus! What is going on? I still get a positive opk every month but I’m just dry when we have sex. Is it ph balance? So weird.... I feel like when we have sex i don’t ovulate and months that we don’t everything looks perfect.. 😟