Relationship gone wrong

I feel so beat up my daughter just turned 1 month . Found out her father was fooling me all this time through my pregnancy telling me we were going to have a life together, but apparently he is married I found the lady and called to see who she was and said they were married 15 years I was devastated. But it seem like she wasn’t shocked. Apparently she forgave him or something because he doesn’t visit the baby he keeps telling me that is difficult for him. They don’t have kids together . My daughter is his first baby. He cheated on her through out all their marriages . I feel so lonely with my daughter