Late on period but negative test

<a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow app</a> says I’m 3 days late, but the Flo app says I’m 6 days late! Just took a pregnancy test (only a cheap one from home bargains) and it was bfn. Did anybody else test this early and get negatives but were actually pregnant?? X