Do you and your husband have other children together?
I can't help but wonder, if during the time boredom was enough of a reason to leave your husband and persue another man, had you worked on your marriage, none of the other consequences may have even happened. But, that is a moot point now, and one that you've probably thought about yourself.
That being said, whatever the reasons are for leaving your marriage in the first place were, I see nothing in your post about having addressed that. Simply returning to the marriage, doesn't fix anything. You are back where you were, only now there is a baby, and the baby's mother added to your life, that will be a tie that will last for the next couple of decades.
For the sake of all concerned, I urge you and your husband to get into therapy, and work through all the confusion and anger. That you are thinking he should have nothing to do with the mother of his child tells me that you aren't yet in a place where you can accept any of it. Your life will change dramatically, and I do not see where you are ready to accept these changes.
Things will never be the way they were. You may always have regrets over your decisions that set this whole thing in motion, but you can learn how to live with the changes you are now forced to accept.
Babies are needy, demanding, and expensive. I hope that you and your husband can work through this together, and all the adults involved, will put the needs of this child, first.
You have your work cut out for you.