If he's watching porn, then he has cheated on you. God says that if any person looks on another with lust in their hearts, they have already committed adultery. And on top of that, he's lying to you and being hurtful. If he's committed adultery by watching porn, then you can believe he's probably committing it with the women he meets on the street. :/ I suggest you get yourself tested for any STD's, and stop having sex with him altogether. The LAST thing you need is to bring another kid into this sham of a marriage.
Have you tried counseling? Is HE willing to try counseling? Or is he content to keep living like this, ruining his wife and kid's lives along with his own? If he doesn't want to change, he won't. And you can't change him, and a counselor can't change him, even GOD can't change him UNLESS he WANTS to change and stop this horrid behavior. If you have tried everything and nothing is working, then do what's best for you and the kids and divorce this guy. You and those kids deserve alot better than what you're getting now. I guarantee God will bring something better into your lives.
As far as hubby goes, if he prefers to stay and do what he's doing, then his life will be miserable, so don't let him drag you and the kids down with him.