Need help. Who is the father?

[lulu865]

I found out I was pregnant at the beginning of August. However, while my ex and I were broke up, I slept with someone else on July 16th. He did pull out and I did just come off my period 3 days before so I assume I wasn't ovulating yet. I typically know when I'm ovulating, and it’s normally a week or so after being off my period. I had a period July 9th till July July 13th. I got back together with my ex the weekend of July 16th and was with him about every other day from that point on, we did have unprotected sex and he did come inside of me. We had been trying to get pregnant for 2 years. I was told when I went in for my ultrasound that I had just got pregnant and that I was really early in pregnancy and they couldn't see a baby on the ultrasound yet, this was August 11th, they said the ultrasound was around 4 weeks pregnant. When I look at the conception calculator, both my due date and LMP show that I would have gotten pregnant on the last week of July. Does this sound about right? If this is correct, then my current boyfriend would be the father. Any advise would be appreciated.

[lulu865]

Thank you!

[AnnieBrooke]

If you had an early ultrasound that gave you an April 21 due date and especially if the due date has not changed over more than one ultrasound, you would have gotten pregnant in thee end of July and the sex on July 16 wouldn't have had anything to do with it.

[lulu865]

August 11th I went in because I was bleeding some and got concerned so they did an ultrasound. They said based on my period being July 9th that I was 5 weeks but looking at the ultrasound I just got pregnant and they subtracted a week so I was 4 weeks then. I went back on August 27th for my "real" first ultrasound and I was 6 weeks then. They said my due date was April 21st at that point. I'm now almost 19 weeks and the due date has not changed.

[AnnieBrooke]

The only problem you would have is if you got some errant sperm from the guy on July 16 (it can happen whether he releases in you or not) and it lasted until around July 21 or so (which sperm can do).  It's not a very strong chance that even if this happened it would have met up with an egg from you, since your period began on July 9, but it's not totally impossible.  However, the ultrasounds do help to pinpoint things.  What due date did they give you, and how early in the pregnancy did they tell you a due date, and was it computed from the ultrasound measurements of the embryo or just from a little wheel or looking on a calendar?