Your husband has a problem with porn, like most men, they want to quit, but the internet is so easily accessible, it is extremely hard for men to quit.
You and he need to address this problem together, he has to want help in order for it to be effective. You can Google it as well, there are many sites with helpful tips.
The problem with porn, is men try to deal with that problem on their own, they do NOT confess one to another as they should, therefore because they try to deal with the porn problem their own self, it is very rare that they succeed. You knowing about your husbands problem is big plus. Now both of you can work on it together.
Whenever i get an email from men who have porn problems, i tell them that i can help them, but they have to do what i tell them to do, step by step. When they agree to do it in order to get help from porn addiction, this is what i first tell them to do:
1) TELL YOUR WIFE.
Then it is rare i hear back from them again. In order to get over the porn problem, one must be held accountable for their actions. If the wife knows there is a problem, she can and should keep tabs on her husband. The husband should agree to parental controls on internet, should agree to the wife monitoring his internet activity, they will agree to do this, if they know they have a problem and the wife is only trying to help.
Now advise to you. Do not take it personally. Your husband is in bondage to porn, its not because you are less desirable, it is not because he does not want you sexually. Anyone who is addicted to porn wants to see more and more, it is never quenched, there is always something NEW out there to see and be turned on by. Many who have porn addiction, feel guilty about having sex with their own wives, because they have to visually imagine porn to accomplish Love making. They have a problem, it is NOT YOU. If you start thinking it is YOU, it will only hinder the healing. Realize that it is a disease and he needs your support and help, NOT your jealousies, NOT your looking down on him, NOT your disappointment. He needs your help, your support to get healed from this, look to Jesus for Help, and if your husband is not a Christian, it is not very likely he will ever stop looking at porn, he has no reason to stop.
satan uses porn as his number one silent weapon against men. And it seems now even more and more women are getting addicted to porn as well. i say silent weapon, because it is a sin people do, that is done in secret and can be hidden from others that it is being done. Silent, Deadly, and it eats souls up.
i know a woman who works at an Adam's Mark Hotel. And she told me, that when the Promise Keepers comes into town and Hotels are booked up for miles around, they have more porn rentals than any other time of year. Promise Keepers is a program to and for men, to teach them about being better dads and better husbands, yet because they have hotel rooms, and there are no wives and no kids there, they Rent PORN.
Porn addiction is a serious problem, because many men have it, and nobody knows it. Read all the sites you can, you and he work together to get this disease fixed, the medicine is Jesus and your support and your love.
Hope this helps.
^i^ Responding to OP