If it’s negative and stays negative with in the time limit that it says on the box then it’s a negative test. A test can’t become positive after the time limit especially if it’s sat over night it’s just a negative test, take another one in 3 or more days.
Positives are only accurate during the time frame given on the test. If it’s out of the time frame it’s not accurate
Wait do you mean you took a test and it was negative but turned positive the next day?
That's a false positive. And test should not be considered valid after the time limit. Especially the next day. I thought you meant you took a test one day and then another test and got a positive, read it wrong.
Not exactly sure what ur question means but Since you don’t know when you ovulated you won’t know when your period is due. You could be testing too early.