Late positive?

Brittnee • Mama to two boxer pups, three angel babies, and my perfect rainbow baby boy born 8-4-21🌈💙

Has anyone taken a test and it be negative then go back and look at it later and have a slight positive sign and turn out to actually be pregnant? I know they say tests are invalid after a period of time but just wondering if it took anyone longer to get the positive and it be a true positive after the time frame