Paternity Help

I know this is going to sound bad, but I have to turn to help.  I have been with a man for 2 years and I found out March 29th that I was pregnant.  We were off and on for the previous 2 months and I had a drunken night and slept with a man on February 17th and March 17th.  I know I had to have had my period around February 20th (because I know I would have freaked out if I didn't).  The ultrasound at 20 weeks, July 16th said I was 20 weeks pretty much to the day.  When I count back it's around March 5th for the conception week/time period.  When I went in at 24 weeks, they said I measured 24 cm at 24 weeks and I was right on track.  Well, daddy has had a turn about him and wants a paternity test when my son is born.  From all calculations (I've googled everything, from conception dates, to fertility dates, etc.) it doesn't seem possible that it would be the other man's, but I am scared to death and am in need of a bit of guidance.  Any suggestions, etc?  Thanks so much.

[RockRose]

I don't think you're counting right.  When I count the weeks I come up with a conception date of March 12.  

When you say you're 20 weeks pregnant,  you've actually been pregnant for only 18.  They begin counting your weeks on the first day of your last menstrual period,  so you actually get two "free" weeks.  You're 4 weeks pregnant when your period comes due.

Too close to call.  I think a paternity test is the only way to know.

[paternityhelp]

So when I asked my doctor about conception date she said around March 9th.........Plus, on March 18th (the day after St Patty's Day) I was super hungover and could tell my body wasn't right, and I felt like I was pregnant already then.  In addition, when I calculate the fertility dates, etc, it says I was fertile from march 2nd to march 9th...........and that March 17th would have been the first day I could possibly see a positive pregnancy test.......

[paternityhelp]

My due date is 11/30....

[RockRose]

Okay.  When I calculate backwards from your due date of Nov. 30,  I come up with March 9 conception date also.

But when I calculate backwards from you being 20 weeks pregnant on July 16,  the conception date is March 12.  So I'm not quite sure where the discrepancy is,  but March 9 would give you a pretty comfortable margin if your periods are really regular.  March 12 is not enough margin to even really guess.