Negative result day before af...

Bridgette
Is it possible if you are extremely regular at 29 days that a day before your period you test negative and it still be a positive? Used a dollar tree test and there isn't a hint of a line. I have felt prego for the first time all month. This is my 5 month trying. I'm super emotional about all this. No idea when I o'd as hubby doesn't want me to "waste" money on it.