I had sex with one guy on the first day of my period which was on August 11. He wore a condom. Then I had sex with my boyfriend on August 28. It was unprotected, so I took an emergency contraceptive pill right away. I got pregnant. I had an ultrasound on September 25 that said I was 5 weeks pregnant. I had to have an abortion due to physical complications. So who was the father of my baby? I was not together with my boyfriend at the time. So please don't judge. Thank you so much for answering.

There is no way to know.

https://www.askmehelpdesk.com/pregnancy-new-motherhood/when-did-conceive-770717.html

Without testing the DNA it is impossible to tell who the father was.

And what does it matter if you already aborted it?

Doesn't really matter at this point does it?

Dating, especially in the first little bit is dicey at best and the date they give is usually to the beginning or near beginning of your last period not the moment of conception or implantation. So the 5 week date could be your current boyfriend. Sperm could stick around so it could be your first fling. Unless you did a DNA test of the fetus that can out during the abortion, there is no way to know for sure and the odds are even for both men.

There is no baby, the baby was aborted. At this point there is no way to determine who was the father.