HELLO, please help !
My LMP was on September 5th and finished on September 10th, my cycle is 26-27 days. I had sex with partner 1 on 13-16th and then again on 27-29th. I also had sex with partner 2 on 20th. I'm pregnant and who is the father?

The only way to know is to have a DNA test after the baby is born. The dates are far too close together to even be able to make a guess.

It is either partner 1 or 2, estimation of conception dates is give or take one week at very best, but is often up to 2 week estimate.

So it could be either, you will have to do DNA test after child is born