Could I be pregnant

Ok so I’m on a 28 day cycle .... my cycle was from oct 19- oct 24. My bf and I had sex on oct 28 I was at a 10% chance of becoming pregnant according to this chart on the app... and haven’t had sex again until today because of the way he work and me in the end Of nursing school we hardly see each other... my questions is my cycle isn’t due until nov 16 I’m wondering if I could be pregnant .,,🤷🏿‍♀️ I have been experiencing extreme headache . Sometime accompanied with nausea, and lower back pain 🤦🏾‍♀️🤷🏿‍♀️ or is it way to soon to tell at the moment we are hoping for a positive test though