He is the only one that can change himself. By getting back together with an abuser you aren’t giving them any consequences. The only way he will ever change is if he has to. “Saving” someone is no reason to stay in a relationship, you can’t just stay because you can see what he’d be like if he changed. He’s not going to change unless he wants to, and sadly you’re probably not going to be the reason, and rarely does adding a baby do any changes.
Next time anyone reading this agrees with going back with a physical, or mental, or sexual abuser just try to think of when the good times happen. Most of the time he’s at his best after a fight happens. That’s called the honeymoon stage, because they butter you up to make you feel dumb for getting mad or to make you forget it and think they can change.
If you see nothing wrong with how they are treating please go get therapy. For your own benefit.