H.S.
I knew I was pregnant 10 days before I was due to start. Everything about my body felt different. My sense of smell had changed already when I smelled certain foods that I would normally like, they made me feel sick. My boobs weren't just tender, they were on fire. When I would take my bra off at night, it would almost feel painful at first to release them.
If you have a 21 day cycle, and you had a period Sept 11th, I would think you could get an early detection test turn positive by the end of the week. Good luck!!!