If there was penis-to-vagina contact with guy 1, then you should at least do a DNA test with guy 2 when the baby is born. Everyone involved deserves to know the true paternity of the baby.
Once you have an ultrasound, and in this situation I would not wait even a week to get one, you can take the estimated due date they give you (the EDD) and put it into an online calculator and see how far back that takes you. It will be impossible (now that you are in your 11th week) to split the difference between the 25th and the 27th, since both guy's sperm (if both guys' sperm were there) would still be viable on the 28th, but if it were to indicate that you conceived later than either of those dates, like the 1st or 2nd, it would suggest guy 2. Don't wait on this if you want to use an ultrasound for this purpose, because some doctors say an ultrasound's margin for error is as large as a week once you are out of your first trimester.
Thanks for your answer. It's a scary moment and just realized it even happened 11 weeks into my pregnancy, but i have a strong gut feeling its guy 2. I could be over thinking the situation more then i should. I mean guy 2 didn't deny it. Guy 1 would and say we never had sex. Cause like we didn't.
Hi, Ariel, well, you don't say what "fooled around" means. If the head of his erect penis never touched your bare vagina, you can assume he is not the dad. If it did (whether he 'put it in' your vagina all the way or not),well, if you are doing any reading, you are probably finding out that in some circumstances the pre-ejaculatory fluid that is coming out of the guy's urethra once he gets an erection (but before he has an orgasm), can have sperm in it. I think the correct explanation is that it will, if he has ejaculated recently. I don't guess you know if he had recently had sex or masturbated when the two of you had the moment on the 25th, but if he had (and by now I'd guess he wouldn't remember either) there is the chance some sperm made it to your vaginal fluids. Again, that is, if you were in skin-to-skin contact 'down there.' (Whether or not he inserted his penis.)
That all said, just a touch like this would not be an easy way to get pregnant. There would have to be sperm and enough vaginal moisture to provide a lubricated way for the sperm to swim upward not exposed to the air. If you think there might have been, and don't have any way to know whether he had recently orgasmed (or if you know that he did), then you have to leave the door open to his being the dad. Even if you ovulated on the 28th, his sperm (if it got into your reproductive tract) would still be alive and waiting for your egg. Unlike the egg, sperm can live 5 or 6 days.
Trying to calculate when your ovulation comes based on the first day of the last period is a pretty iffy method. Some women ovulate on day 8 (and have a 20-day cycle) and some ovulate on day 18 (and have a 32-day cycle), so calculators based on a neat and regular 28-day cycle don't do a lot unless you know that is true of your own cycle. You are right that an ovulation calculator that is simply based on dates would say you ovulated on the 28th, but that all depends on how regular your cycles are.
If the sex with the first guy was just some contact of penis and vagina but not full ejaculation, and you think he didn't have sperm in his urethra or on his penis from an earlier activity, and if sex with the second guy was regular unprotected sex and he had an orgasm when inside your vagina, of course the second guy has better odds. However, you are going to need a DNA test when the baby is born. It would be unusual to get pregnant by such a fleeting contact as you seem to describe with the first guy, but stranger things have certainly happened.
I assume you will keep the baby in any case? If so, get a DNA test with both guys once the baby is born, and go to a lab certified by the family courts for this purpose (no drugstore tests). Too many lives are riding on you knowing the correct answer.