Late period

I have postponed my period due date on glow several times... Still getting bfn as of yesterday, but have symptoms not related to af--- wonder how long I should go if I don't get bfp and if anyone knows if glow gives advice on their notices if you keep marking late period.  I'm usually 33-35 days and today is 37 days.  The wierd tho g is I've tested positive three times on opk - jan23 , feb 4 and 10th - so I guess I'm not close to a test mark for dpo on the 4th or 10th--- any thoughts to my blabbering story?