Hello
Thanks for writing to us with your health concern.
Firstly, I would tell you that even early first trimester
ultrasound scans have an inherent error margin of upto a week.
That means that based on the sonogram results, you cannot reliably pinpoint your dates of conception.
The two sexual encounters occurred on dates which are too closely set together.
There is no reliable method to say which man is the father, apart from DNA testing.
Yes, the likelihood of unprotected sex resulting in a
pregnancy is much higher than the protected sex encounter, but you run the risk of never knowing for sure , unless you go for paternity testing.
This can be done as early as 8 weeks of pregnancy, by non invasive testing from the blood.
Also, it can be done by invasive testing -
amniocentesis.
The non invasive tests are also 99 % reliable, so you can go for those.
You would require sample from only one of the partners, so that it can be conclusively established whether he is the father.
Please go for the testing instead of living with uncertainty all through.
Take care.