Due Date Keeps Changing

[skyemarie0529]

My due date keeps changing every time I go to the dr.'s and it's driving me crazy because I don't know who the father is. I was sleeping with the guy I was dating until October 19. We broke up and I slept with another guy on October 21. When I first found out I was pregnant the dr. said I was about 8 weeks along. That wouldn't be possible though because that would put my conception date the week I was on my period (first week of October) and I didn't have sex on my period. Due date then was around July 4. Anyways that would've been guy #1. I went back on January 2 and had another ultrasound and the dr. moved it back to around July 7. He made sure to say these were all approximate though. This would still be guy #1 though. When I had my gender ultra sound in February my due date got moved back again. This time to July 12. That would mean I ovulated October 19. At that point it could be either guy #1 or guy #2. I'm so confused. I know I'll need a DNA test but I'd like a little peace of mind. Please help!

[AnnieBrooke]

From your first ultrasound, I get the probable date of ovulation of October 11.  I would not bother to try to figure out any dates based on an 18th or 19th week ultrasound, the margin for error that late is a week or even two weeks.

[skyemarie0529]

July 12 was given to me at my 18 weeks 5 days ultrasound (using that due date). The last one given to me before that was July 7 (which was at 12 weeks 5 days using the July 12 due date or 13 weeks 3 days using the July 7 due date). Is it all too close to tell? I'm planning on having a DNA test anyways but for my own peace of mind I'd like some reassurance.

[AnnieBrooke]

When was the July 12 date given to you in terms of the weeks duration of the pregnancy? If it was later than the 12th week, it could be a week off or more.

[skyemarie0529]

I had done a little research online and for a July 12 due date it said the probable date of ovulation was October 19 but possible dates of conception were October 15-23 so I was just really confused.

[AnnieBrooke]

Only early ultrasounds are reliable for dating purposes [the later in pregnancy they are, the wider the margin for error, since babies grow at different rates].  Besides that, if the only time you slept with the second guy was October 21 and you are taking from the changed due date that you might have ovulated on October 19 (a day when you had recently slept with your boyfriend), I don't actually see why you think October 19 "could be either."  The egg only lasts for about 24-36 hours after ovulation, and then it disintegrates.  

[skyemarie0529]

The only time I slept with the second guy was October 21. Other than that it was the first guy. This was all unprotected. I'm just worried because with the early July due dates it should be guy #1 and that's what I was thinking for the first 19 weeks of my pregnancy. Then I went for the gender ultrasound and it was moved back to July 12 and that is the one my dr. is sticking with. July 12 could be either so for the past 10 weeks I've been going crazy.

[AnnieBrooke]

Skye, if that "puts your conception date the week of the period," that actually makes sense because doctors begin the date count of pregnancy (8 weeks, 10 weeks, etc.) on the first day of bleeding of your last period, not on the day they guess conception happened.  If a doctor told you that you are "x weeks pregnant," he or she was counting back to the presumed day 1 of your period, not to when you conceived.