Sex on 1st day of fertile period.

My husband and I had unprotected sex on September 30, the first day of my fertile period. What are the chances, really, when the app says something small like 9%? Since then, I have had one bad headache, which I vomited from, increased thirst for a few days, some breast tenderness, and increased appetite. No spotting. If I were pregnant, would I be having more pronounced symptoms at what is now over three weeks? Could it be? Period is due this weekend. Anyone with similar experience?