Pregnancy Timeline & Conception Estimation: A Detailed Analysis

Question
Hi im 24 yrs old and I've been with my boyfriend for 4 years. During the month of September we broke up for about a week and within that week I had slept with someone else.My last period was August 31st 2005. I normally take birth control but that month I started it 10 days late bc I was on vacation and did not have them with me. I took them on September 18th and doubled up on pills to try and catch up. I had sex with this other guy on September 24th. I've had a sonogram done but I didn't tell me my gynocologist that I slept with someone else at the end of September. I asked him when I would have conceieved and he said right smack in the middle of September and said me starting the pill on the 18th did nothing cuz i would have ovulated already. Is he accuarate on this?

Answer
If your last period started on August 31, and you were ten days late in starting your pills, you probably ovulated on September 14 and could have conceived if you had unprotected sex on September 13,14,15, or 16. If you started the pills after September 14, they would not help because you already ovulated. However, since you probably ovulated on September 14, you could not have conceived on September 24 because it was too far away from ovulation.