Who is father of my baby??

I was curious.. I had sex with a guy back in dec around the 6th or so we used a condom the 2 or 3 times we had sex each time. My period came on dec 18th it lasted the normal 3-5 days for me. I had sex with my ex twice unprotected within a two week span at end of dec obviously after my period was gone where he came in me. The second time was the 31st. I then had sex with another guy on the 1st using pull out method. I was on top. I took a pregnancy test about a week after missed period I think around jan 25 or so. I went date of to ob around vday in feb n she went by last period n said I was about 8 weeks along n gave me a due date of sept 23 which was the exact date my baby was born.. I had asked ob at wat point in time did she think I had conceived n she had said around end of dec beginning of jan. I have assumed it was my ex bcuz of him cumming inside me. Now she is here she even resembles him a little.. we are gettin a dna of course I have told him theres another possibilty. I have told guy on jan 1st he may b possible but I was 99% sure he was not that it was my ex.. Both have not been supportive.. The ons simply bcuz I believe he is not the father.. I have been stressing that I am puttin this on my ex n he could possibly not be her father.. Do u have any helpful advice?