Confused about ovulation test...

Tiffany

Today is supposed to be my most fertile day and I am supposed to ovulate tomorrow, according to this app and according to one other app I use. I have regular 30 day cycle periods and always starts my period either on the 2nd or the 3rd of the month. I have been having egg-white CM and slight cramping. But I just took an ovulation test and it said negative... confused as to why?