Sooooo confused

Hi guys!

I have a 39 day cycle but according to my apps I ovulated a week later then my OPKs said. My husband and I TTC when I got positive results on opk and now it’s been 6 days but got a negative preg test although I’ve had fullness and cramping ever since I ovulated. I read online today that I shouldn’t test until near my period which is still 2 plus weeks away! How do I know when to test?