Late period

Jess

My period is 9 days late according to the <a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow app</a>. I marked my last period with this app so I figure it’s pretty accurate! I’ve taken 2 pregnancy tests which both came back negative. The tests I took were First Response with the 1 or 2 pink lines. I don’t think I’m reading it wrong, only 1 line was present & it was pretty dark. So perhaps i should take one that says “Pregnant or Not Pregnant”? Suggestions?? I’m just confused at this point lol. Thanks!