Trying for 3rd baby

Just started trying for baby number 3 on the 25th of February and well I never have missed a period and now I’m 3 days late but pregnancy test are negative …we had s£x on the 25th, I don’t know when I ovulated but app says 19th

Could there be a chance the app wrong?

Like I ovulated late and now I should wait to test on the 11th since that will be about 3 weeks since s£x