So sick, pregnant?

Samantha • 24 yrs old, married, stay at home mom of a five year old and one year old
I'm ttc #3, I'm 13dpo and my AF is due tomorrow (Feb 4th). The last two days I've been so nauseous! It feels like the morning sickness I've had with my first two children BUT I took a test on Sunday and this morning and both were BFN. Is there a chance I could still be pregnant?