September 1st is my due date what is my conception date? The doctor told me I conceived around the 5th to the 11th of December but I did have sex with another man but we used a condom on the 18th of November but was regularly having unprotected sex with my boyfriend. I also have short irregluare periods so I do not know my last one but I am pretty sure it was in late October. The doctor told me I was 6 weeks at my sonogram and he said he was pretty confident with my conception date he told me... do I have anything to worry about?