The mood swings and arguments really start to take a toll in these relationships, especially with the added responsibility of a 1-month old child. It's a time of change and transition.
You will need to be strong and stable for yourself and your child. As others have suggested, the Lessons are a great place to start. There are a lot of things you can do on your side of this relationship that will give you back control and help keep you strong.
Are there specific issues that cause trouble? Is he in treatment?