My First Day Of My Last Menstrual Period Was 12/27/12

my first day of my last menstrual period was 12/27/12 i had intercourse with the same person on 1/2/13 and on 1/8/13 with one man and then 1/11/13 with another I had a blood spot on 1/13/13 which to me was implanted becaue after that i never got my period and then did the pregnancy test and it was positive now I am confused on knowing who is the dad I also gave birth on Oct 7 2013.