My due date is dec 24, according to the conception calendar I conceived between 3-29-4-9 with a ovulation date of 4-2, I slept with one guy on 3-25 and the other on 4-4. Who's the father?

Either one. The dates are too close to be sure. Calculating conception dates is an inexact science and can vary by more than 2 weeks either way.

The only sure way to know is with DNA testing after the child is born.