Hi, it sounds like the first guy is the dad, like you conceived around December 7. If the baby is here, what is stopping you from getting a DNA test? Then you won't have to live with the what-ifs.
Unfortunately I did my first scan very late, 1st scan 3rd April 19weeks due date 28 August , 2nd scan 2nd july 29weeks due date 17 September, the doctor said the baby was really small plus i was hardly showing at the time. 3rd scan 15 August he just said I will be due in two weeks time 30 August