How will I know?

Mallory
17 yo female, 110 pounds, 5'3.
My boyfriend and I have been having sex nearly every day since May 13, the second day of my period. We do not use condoms, but instead the pullout method. We use several different positions and often he will ejaculate more than once. What Are the chances of my getting pregnant if he used the pullout method, and is it possible that I could be already? How will I know if I had sex while on my period? Any advice and thoughts are welcome!