Just to add my last period was the 26th-28th of February and we had sex on 16th and 17th of march. I would've ovulated around the 20th?? My midwife isn't convinced by the scan dates and thinks I'm closer to 14 weeks than 13 weeks. I also have a history of having small babies if that helps.
OK, you are saying,
- first day of last period: February 26 (cycles approx. 37 days long)
- sex with first partner regularly until March 17
- spotting starting March 26 (two days)
- sex with second guy April 2
- sex with first guy April 13
- ultrasound tech says conception April 3
- from February 26 period, next period due around April 4 if cycles are really 37 days long; if you count the spotting on March 26 as a period, next period due May 2, and ovulation would be expected April 19 from that. (Frankly, I would throw out all the assumptions based on when your last period was, you have irregular cycles.)
So, the big question is, when did you get the ultrasound? And did the ultrasound tech say "conception" was such and such a date, or did she say you are x weeks pregnant?
Well, sweetheart, I see what you want, but even adding a week to the ultrasound estimation of when conception was is not going to make your boyfriend the father. You broke up on March 17, right? The good news for you is that because your ultrasound was in your 12th week, it's possible for you to be a week further along than the ultrasound suggests, due to variations in the growth rates of embryos. (When using an ultrasound to try to determine conception, at 12 weeks GA doctors usually will say there is a margin for error of +/- 7 days.) Some babies grow faster and some grow more slowly than the average growth curve on which ultrasounds are based. (By the time a woman is in her 40th week, an ultrasound can be up to three weeks off if used for trying to determine when she got pregnant. But not in week 12.) This means that you have a possible conception range of from 7 days earlier through 7 days later than April 3.
Unfortunately for hoping your boyfriend is the dad, you and your boyfriend's last sex before the breakup was March 17. Even if you move your conception date back the week suggested by your midwife from the April 3 estimated conception date given by the ultrasound that measured the baby, that only takes you back to March 27. And even adding a further margin for the 4-6 day life of sperm in the woman's body still only takes you to March 21 or so. It takes some wishful thinking not supported by medical science to stretch this even back to March 17.
One thing you can do is see what the next ultrasound indicates about whether the baby is growing faster than the average or not. If it also points to December 25 as the due date, that would suggest your baby is not growing faster or more slowly than average. If your baby is not growing faster than average, then the idea that you are really a week further along than you think is probably incorrect, no matter what the midwife could feel with her hand. And if your baby is continuing to match the averages and the conception date keeps coming up as April 3, you would have to be ready to hear that the other guy is the dad. But if your next ultrasound gives you a different due date than Christmas, it might mean the baby is growing at a different rate than average, and then you could hope the first ultrasound was also affected by the baby's rate of growth being off the average. You would have to extrapolate which direction (whether the baby is growing faster or slower than average) by what due date you get.
If you absolutely need to know for sure before the baby comes, Ravgen and the DDC do accurate prenatal DNA tests (non invasive), at a cost. If you go this route, don't go to a cheapie so-called lab advertising on the Internet, go to only one of the two I just mentioned. And in any case (DNA testing now or DNA testing after the baby comes), be sure to witness the guys doing their tests and be sure to test with both guys. That is the best way to know, since one guy will get a yes and the other guy will get a no.
A period tracker app is an automated calendar that intakes data from prior cycles and makes guesses. If your cycles are not regular, anything can happen the following month, and the tracker is pretty much just guesses. If the ultrasound, which saw and measured your actual baby, says you got pregnant April 3, it is pretty hard to turn that into March 20 just on the basis of a period tracker.
Can you afford the big price of a prenatal test? At least you would know early. Ravgen can even do a 'discreet' test, using a swab from the guy's drinking glass or glass of wine. You could test with both guys that way without telling your partner, and would only have to tell him bad news if there really was bad news.
OK, believe it or don't. But what else do you have? Sitting in fear for the rest of your pregnancy and not believing anything your doctor or midwife says? You should at least be making some plans about what you are going to do when the baby is born. (Hint: It cannot be hiding the fact that there is a question. That would be immoral to all concerned, and the truth will someday come out anyway. People take DNA tests for fun to learn their heritage. How would your child feel to get this news at age 20, and you never told him or her?)
Anyway, the parts where your story cannot be answered for certain due to the limits of research are:
- How long does sperm last in the woman's body for sure? Much research says 4-5 days. Some says up to 6 days. Some says it can even last longer, but that sperm is not strong enough to penetrate the egg after about day 5 or 6. But there is no DEFINITIVE research that says "absolutely." (And how could there be, there is certain to be variation among men.) So, maybe you can say to yourself that his sperm is of the longer-lasting kind.
- The part about the margin for error when there is a fast-growing baby. Doctors say +/- 7 days at 12 weeks, and +/- 3 weeks at 40 weeks. But how well has this been tested? Do we KNOW it might not be +/- 10 days at 12 weeks? Because all you need is about 3 or 4 more days and your boyfriend is back in the mix. Especially if he has long-lasting sperm.
Regarding that Internet DNA test, did your boyfriend send in the swab himself? (Internet tests can readily be done fraudulently, if a woman wants to substitute swabs or even falsify the report.) If your boyfriend has a possible child out there, he should seriously insist on a DNA test done at an official lab (not a cheapie one done by mail) and the sooner the better. Because she could come back to him for a LOT of back child support sometime. I have heard horror stories of guys getting hit years after a child is born for child support for every month the child was alive. He should know for sure now, and should do this with the help of a lawyer, and should go to a lab certified by the family courts for legal determination of paternity.
One other possibility that might help you sort this out is if the baby is a girl. If your next ultrasound shows this, write me back. It would be a point for your boyfriend.
Finally, you need to decide what you are going to do if you wait and just do a DNA test when the baby comes, and the wrong guy is the dad. I would put the screws to the ex for child support, myself, especially if he is just a cad. But if you don't want him in your life at all, I think you can also write off his obligation to child support in exchange for him never wanting a relationship with the child. You should see a lawyer and a counselor also, to be prepared to think over what you want, if that unpleasant possibility becomes a true fact.