Question about pregnancy?

First off, I want to say that I am a guy and don't know a darn thing about pregnancy and how the female body works. I tried Googling and doesnt work for me. LOL Anyhow, my ex and I were together for a while in 2008. We have a beautiful daughter together but I have lingering questions in my brain that have been boggling my mind for the last 2 weeks. Our daughter was brought in by C-Section on June 8, 2009 (a week early but she was full term) . We are estimating that we had 'boom boom' in or around her birthday on August 18 (+/- 2 days). A few days prior she said that she just got off her period. She had told me that she went to a pregnancy center in the middle of September (12th - 15thish) and told me she was pregnant. But doing all these stupid calculators online are giving me headache and are not giving me an accurate enough date of when it could be because I have no idea what an LMP or ovulation or conception is. Points to the first person that can give me a pretty accurate timeline. :-)