I am due August 6th 2012 by an early ob ultrasound. My LMP was October 31st which is equal to how far along I am. My cycles have always been a little off. I had sex on November 18th, even though the guy says he didn't in me. On November 25th, I had sex and this partner pulled out. Which date is more possible to be the conception date?

Way to close to tell, there is no way at all to determine a conception date within basically a week period. Either could easily be. Pull out is no real method, it easily fails and there is sperm often in the early fluids.

So you will just have to wait till the baby is born and have a DNA test done to make sure who the father is.

Conception dates are an inexact science the only way to tell for sure will be a paternity test AFTER birth.

Also the withdrawal method is a highly suspect method of birth control. So I wouldn't count on it as an indication of who might be the father.