pregnancy scare

So on september 5th i had period sex for the first time (do not recommend lol) my boyfriend nutted in me but it was my third day technically my 2nd day of my period . i usually ovulate on the 17-20 one of those days and between. what are my chances of getting pregnant? i took a pregnancy test 3 weeks after the 5th and got negative. the catch is i started my the pill on the 22nd of september so it delayed my period i until my sugar pills. should i retest? and what are my chances?