My cycle the month before I got pregnant was 29 days, the first day of my last period was Oct 9, 2009. I am now 8 months pregnant and scared because I had sex with my exboyfriend around the time me and my Fiancé conceived. I have all the dates wrote down in my planner so here it goes, me and my Fiancé had unprotected sex (he came inside me) on Oct 16, 17, 18, 22, and 24. Me and my ex had PROTECTED sex on the 20, and he pulled out before he "came". What are the chances that our little girl is not my Fiancés?

Let me see sex total 6 times, one out of 6 is what about 18 percent. But then it is exact time you were the most fertile, the sperm count of both men and more.
* pull out is not a method, plenty of sperm in early fluids****

And there is no way ( NO WAY) to make it even within a week, it is merely estimates. So no way to know till the baby is born and you get a DNA test done