Pregnancy Timeline & Paternity: Estimating Conception Date

Question
Hello I wanted to know if you could tell me what date of intercourse most likely got me pregnant?

I had sex on 12/12/12 with one partner and sex with another on 12/16/12.

I found out I was pregnant on 1/7/13 the Dr. said I was 5w 5d.

My last menstrual was 11/28/12. I know the first 2w of pregnancy are calculated before conception takes place.

Who is more likely to be the father? I ovulated on 11/14/12 and 12/13/12 according to my period tracker.

Please Help, thanks.

Answer
It's too close to call without a paternity test.  Sperm can live in the reproductive tract for up to 5 days and the dates of intercourse are only 4 days apart, meaning that either man's sperm could have resulted in the pregnancy, especially if you ovulated later than the 13th which could be a possibility without an early transvaginal ultrasound to verify dates.