My monthly cycles run 26 days, my last cycle was 3-15-2009. I had sex on 3-22-09 I don't think he ejaculated but I'm not 100% certain. I had sex again on 3-28-09 I was ovulated on the 28th or 29th. I missed my period on 4-13-09 took an ept test, it was positive. My question is this: Since sperm can live from 3-7 days what day was the day I most likely conceived on ? The 22nd or the 28th?

If the first day of your cycle was 3/15/09, then you most likely conceived on 3/29/09 and your due date would be 12/19/09.

But it is always a guess for within one week, Unless it was two different men, it really does not matter, due dates are estimated guesses anyway.

If there are two different possible fathers, you will not know 100 percent for sure till there is a DNA test