My fiance left me two weeks after we had our baby girl

I don't know how to deal with this. We were in a long distance relationship. His things were here but he went back and forth because he have to boys back up north. I just gave birth to his first little girl and he just turned into a completely different person. Didn't want her to have his last name so I changed her first name to what I wanted. Initially he came up with her first name and we agreed but then he said he didn't want to sign the birth certificate or give her his last name until we took a paternity test. I tried to go get one done a few days after getting out of the hospital but then he said no. He then proceeded to say that he don't take care of a kid that don't have his last name. He stayed here for a little over two weeks and made it hell for me. I had a cesarean and he wouldn't even help me around the house. Instead he went hanging out and to the club with his cousin. He packed all of his things and left two days ago. I'm so hurt because my baby girl don't deserve this. How do I cope? I now have a 7 year old and 2 week old with no help. He is a great father to his boys, I don't know why he is doing this to our little girl