How Can I Determine The Paternity Of My Child With Details About My LMP, Dates Of Intercourse And The Duration Of My Pregnancy?

.21 years old and i m 25 weeks pregnant now first day of my last period was 12 october and it ended 16 october, I had sex with guy1 on 17 october and he said he ejaculated inside me. I had sex again with guy2 on 20 october he pulled out. Then I had sex with guy3 on 22 and 23 october not sure if he pulled out or not. Then 9 march I went for an ultrasound I was 21 weeks pregnancy. Who could possibly be the father of my unborn baby?