I just don't understand anymore

It honestly baffles me how a man you loved and married and made a baby with can turn around and say it's not his and leave you. Then put off the divorce for 6 months and cause you nothing but stress and anxiety your whole pregnancy. Then has the nerve to ask for updates on the baby after every appointment but still claim it's not his. I just don't get it. I want to ask him what he's trying to prove but when you're dealing with a narcissistic a****** there's no point.