I think he's an utterly selfish man who wants to live life like a young, single man.
I just asked my husband his thoughts and he said:
'Why did he bother settling down and having kids just to act like he hasn't? Why doesn't he want to spend time with his family and children, especially his new baby? He's the sort giving us (men) a bad name.'
Once our kids arrived we became a little team and whilst we'd go away for the odd weekend with friends (never when the kids were that young) the majority of our holiday leave is for family holidays/ time together. I can't believe his family is enabling him to do this.
From what you've said about how he is out most of the week too, I'd be asking myself why I'm in a relationship if I'm ending up being a single parent?
I wouldn't be happy in a relationship like that, I'd much rather be actually single and sharing custody/receiving maintenance. See how often he can live the high life when he has to commit to a custody arrangement and paying for the kids he likes to leave behind!
I'm so sorry OP but I think you've married a man-boy who wants to act like a teen and do what he likes without consequences or a thought to what you're going through. I'd be seriously reconsidering the relationship.