Need some help and advise :(

Okay so I'm am 13 weeks pregnant and I'm dealing with my pregnancy completely on my own I go to all my appointments by myself and I'm always feeling a little down . Me and my child's father was together and at first he was excited about the pregnancy , but when I was about 8 weeks this girl poped up and said that they have been sleeping together and now she is pregnant. Since then I have talked to him twice and he never asks about the baby he just likes to argue with me . I don't want him in our lives and he feels like I'm a bad person because of that ? I'm mentally and emotionally damaged what should I do ? Should I let him be there or am I better off with living my life without him like I am basically doing now ? This is my first baby and the most difficult thing I've ever been threw and I'm overwhelmed all comments and advise will be appreciated Thank you