Men are more visual. They are turned on by attractive women, which can vary across a whole spectrum of body types, appearance, etc. And yes, it is not a commentary on your attractiveness that he likes looking at images of women. However, the fact that he is excusing it as second nature is ridiculous. Men are visually attracted to women. That doesn't cause you to navigate to porn and look at it. That is a choice. When he makes the choice to look at the porn, of course he will be attracted.
It is a problem, but not a disease. The problem is he consistently chooses to look or flirt.
Also flirting is a choice. You cross the line when you decide to cross the line. And that is not even about visual cues. So there is no excuse there. He wants infatuation and the emotional high that comes from these discussions. He hasn't learned to say no and to build up the relationship with you that he needs to.
If he didn't stop when he told you, and he didn't stop when your child was born, he is not stopping until he gets help or has his life crash down on him.
You need to let him know this can't stay secret. His child will eventually find out about it. His church will. His friends and extended family will. It is time to stop making excuses.
He can change this, by removing the porn and flirting. Your relationship can be rebuilt by spending time with you. But those are all choices he must make.
If he is ashamed now that will only increase when folks find out about it and he has destroyed his spiritual and marital life.