Are you already 4 weeks pregnant before missing your cycle ?

So I had unprotected sex on the 9th he didn’t cum in me or anything now it’s literally time for my period which always always comes earlier then the app says and I don’t see any sign of it , mind you every other time I’ve had sex in the past 6 months always used protection and never missed a period, literally took a old pregnancy test I had maybe the other day and it instantly said not pregnant. So now I’m very confused, did I test too early because if I were pregnant prior to before the 9th I’m pretty sure the test would’ve definitely been positive.