13 weeks pregnant. Had normal period on 4/15-4/18. Had sex with someone else before period then someone else after period between 4/19-4/29. Who's the dad?

Sperm from guy #2. Having a normal period means a woman is not pregnant, so the conception has to happen AFTER the last normal period. Thus, the sperm must have come from guy #2. If married, one can also go by the old saying "the father of the baby is the man the woman is married to". The goal is to have a happy, intact family to raise a child in.