My ex got pregnant, we had sex on the 12/3/2016 she was at the end of her period, we broke up and a week later on 12/12/2016 had sex with another man, she got a ultrasound on 2/8/2017 Doctor said she was 10 weeks pregnant, she s 13 weeks pregnant now 3/3/2017 , she says the doctors calculate from her last period she says she conceived on December 12. She say it can t be mine My question is, is there any chance it could be mine?