Either could be the father. I'd be upfront with both and get a paternity test done when the baby is born. Best of luck.
2 days is too close to call....even when you get your ultrasound to date the conception it's not going to give you an exact date. Paternity test by DNA after the baby is born is your only option now...sorry! Good luck, have a happy and healthy 9 months :) or 6 by now LOL :)