idk who's the father .

November 28th I had sex with guy A . Then on December 8th I got my period . The doctors said I was -13w3d(currently) but I also had sex with guy B i can't remember when it was excatly but it was around the 22 of December !! Now the doctor says the baby looks too big and that it they think the baby is 14w6d . Does this mean guy A Is the father . ? Does this mean i got pregnant before or after my period I need seriuse help .