My due date is the 20th of october 2023. i had sex with man a on the 21st of january i had sex with man b on the 25th,26th and 27th (my conception day) who is the father?

The only worthwhile answer & one that will hold up in court proceedings will be a DNA based paternity test. The NIPP is a non-invasive test performed on your blood as early as 8 weeks. They find fetal DNA in your blood & can test it for a variety of things including paternity. Ultrasounds and projected dates can give data, but a surprise at delivery is not worth a wrong call.