I'm super late

Vanessa
Hello, I need help. So I've be TTC for baby #2 and my last period was August 9. Now Glow says I was fertile 3days after I had sex with my hubby. Now I am late , so my fertile days changed . And I had sex again on the 9 of September . AF is expected this whole week but every time I took a test it was negative. Why is this happening .