Why is so painful when u love someone that u have a child with him and u find out ur second baby is…

Why is so painful when u love someone that u have a child with him and u find out ur second baby is not he is that why is so painful right now I wish my boyfriend forget me because what I did but I know he not going to forget it me and that kind of fuck up what he say about my daughter that she is ugly and her daughter is more cutier than my other baby it really hurt can someone please help me to see what I can do about this relationship with my daughter father and me to see if I could win him back.