Hi, what makes you think your peak ovulation day was May 15? Because you have a 31-day cycle?
Did you get your due date from an ultrasound? If so, they would have counted back 2 weeks from presumed conception, not 16 or 17 or 18 days. An ultrasound that says your due date is February 3 is saying you got pregnant on May 13. (Unless, of course, you had the ultrasound later than your first trimester. If so, it has a margin for error that would account for either guy.)