i'm afraid u're out of luck until the baby's born and u can have a paternity test done on your baby. u were obviously ovulating around the 24th, but could have gotten pregnant at any time over those few days. it could be from either guy.
Nope, can't pinpoint the day as you will never be able to tell exactly when that egg released, was fertilized, or implanted. Even early ultrasounds have a margin of error of +/- 4 or 5 days. As the previous poster mentioned, the only way for you to know is a paternity test.
Good luck with everything, that is quite a pickle! I wish you all the best.
Andi