I’m currently pregnant and confused about when conception was. I had a period on august 20-23 and I was taking the contraception pill until around mid September (I can’t really remember day) I then had sex on September 21st which was 4 days after I was due my period. My period was three weeks late so I took 2 pregnancy tests on October 3th and they were negative, I then got my period on October 5th - 8th (my period are always 3 days) then I had a sexual encounter on October 15th but the person didn’t ejaculate he had an issue with his erection. On November 20th I found I was pregnant and I’m so confused as to whether it’s from September 19th or October 15th. I’ve read that people get implantation bleeding and I’m wondering if that happened on October 5th -8th or if it was my period I remember it to be a normal period not light bleeding. I had an ultrasound and they measured and it was coming up as 6 weeks 3 days does this mean it was definitely from October 15th or is there still a chance it could be from September 19th and I had implantation bleeding not a period? Sonographer is saying October 15th makes the most sense with the measurements but with the issue with the erection and it being in for only a few seconds I find it quite hard to believe.