Bringing baby daddy to court

So I had a baby with someone I really love . We dated for a 3 years and then broke up

Bc he cheated on me, and then he recently had a baby 7 months after the one we just had with that girl .

I really can’t stand seeing him with her bc I still do have feelings for him and it doesn’t help when he tells me he has feelings for me still , but can’t act on them bc he’s in relationship .

We didn’t go through court for custody, but I told him I wanted to because I want to take out all of the emotions and feelings out of this. He told me he doesn’t want to go through the court and if we do then he will file for full custody .

He’s literally making it so hard for me idk what to do