No judgment please.. But I need help figuring out who the father of my baby is..?

Ok... So here is the run down.. I can't remember exactly when my last period was.. but I had one around the middle of May.. and then had another one around the end of may/beginning of June.. I would say somewhere between the 30th and the 1st/2nd... I was also on the birth control pill Camilla.. I had sex with my ex (my 18 month old sons father) a few days before the 13th.. maybe 2 to 3 days prior.. We aren't together though it was just a random thing.. Then an old friend/ex of mine came in for a visit.. He lives over 500 miles away.. he is African American (the other guy is white).. We had sex on the 13th, 14th, and the 15th. On the 18th I had sex with my sons father again. The following Monday, which was the 20th, I got a pain (maybe implantation pain??).. again I was on the pill this whole time.. The on Thursday the 23rd of June I took 4 home pregnancy tests.. the first 2 were dollar tree tests and had very faint lines show up.. the second 2 were first response and had very solid positive lines show up.. On Sunday June 26 I went to the ER and had a quantitative HCG blood test done and was told i was about 2 weeks preg.. which makes me think I got preg around the 13th.. meaning it would be the african american guys baby.. right? This is what I am hoping.. i know I messed up and should NOT have slept with my sons dad.. Me and this other guy are talking and pretty much together.. he's been thinking bout moving here or me moving there.. I really want this to just all work out.. Can any one else give me their opinions about who they think the father would be? I know no one will be able to tell me for sure.. but I'm just so stressed out about the whole ordeal.. Also.. Do you think it might be possible to tell on the 4D ultrasound if the baby is mixed race? I read somewhere different races have different skull types.. and that sometimes you can see the features pretty clearly such as the nose and lips.. and maybe even the hair.. Just curious.. Please help if you can! And please no rude or negative remarks.. I already know I messed up big time.. and don't need anyone elses negativity. Thank you so much!