Pregnancy Due Date Calculation: Understanding Conception & Testing

Question
Hi,
I have a question that has been on my mind the entire pregnancy.  My LMP was Oct. 1, 2007 then on Nov.1, 2007 i had some bleeding for 1 day only. That never happened to me before so i decided to do home pregnancy test but not right away i did it on Nov.16, 2007 and it was positive.  When i went to the doctor he completely confused me with the due date and the date of conception.  My question is suppose i conceived on Nov.15, 2007 could my pregnancy test come positive the next day like mine did on Nov.16, 2007?  Or did  i get pregnant way back in October?  And if i did get pregnant in October could November's slight 1 day bleeding be just an implantation bleeding i heard that happens to some women?  
Regards,
Olga.

Answer
A pregnancy test could not come back positive only 1 day after ovulation.  The fertilized egg needs several days just to travel to the uterus and begin burrowing in, and several more days at a minimum for hormone levels to become detectable in the urine.  It sounds more like that you did conceive in October, and the spotting you had on November 1 was indeed implantation bleeding.