due date July 15 based off of ultrasound

Hi I'm so ashamed of myself for this but I had sex September 20 while on my period with guy A then in october I had sex with guy a B on 7, 14, had some bleeding on the 15th(think it was my period Cuz that's when it was due n lasted 3 days) then sex on the 20, 26. On November 6 I found out I was pregnant by taking a test n at my ultrasound it put me one week before my lmp and said I was due july 15. My question is did I get pregnant from sex in September? I talked to my doctor about it and she said it would be sex from October but I just need some reassuring from more people . Thank you