has this happened to you?

Evelyn • 27 | Virgo♍️ | mommy to two princesses 💜💗👑 Married 💍 ❤️
Okay so I was supposed to start AF on the 20th but it never showed up same goes for the 21st still nothing so I deleted my AF from my calendar (on glow) so it recalculated it to come yesterday but no sign of it same goes for this morning no AF  glow now calculated it to come on the 24th. (So we'll see) 
I took a pregnancy test on the 21st and it came back negative. 
If I was pregnant wouldn't it have came back positive when I took a pregnancy test?