Paternity Determination: Understanding Potential Fathers & Timing

Question
The first day of my last period was April 26th. I had sex with my boyfriend on May 7th and some random guy on or around May 12th-16th. I have figured out that I ovulate around May 10th. I'm hoping that this baby is my boyfriend's. What do you think?

Answer
You will need a paternity test.  Sperm can live in the reproductive tract for up to 5 days, meaning that either one could be the father as the dates of intercourse are not more than 5 days apart.  As your likely ovulation was around the 10th-12th, it's about a 50% chance for either of them to be the father.