I'm responding as one spouse of a porn addict to another....I just found out about 9 months ago that this has been an issue for my husband for bout 20 years...our whole marriage...and he kept it a secret...but like you I was suspicious of his lack of intimacy ....but I was too much of a codependant person to confront him about it years ago. Now he told me about it himself and he says he hasn't been involved in that behavior in 3 years. I have been going to counseling myself which started for other reasons and has led me to see that the marriage is the cause of most of my emotional pain. I've talked about the effects of the addiction on the marriage with T. and it led me to develop some healthy boundaries for the marriage. I've just told my husband that he has to go to counseling himslef because even though the "porn addiction" may be undercontrol it has not solved the underlying issues for why he did that....and that he is replacing other addicting routine behaviors in order to feel a sense of control of this problem which doesn't just go away... It took a while for me to get to a place where I could live with whatever choice he was going to make but finally said either go for therapy and deal with this issue and all its root causes or get out. He just agreed to go to therapy this morning.

Here is an excerpt of an article I found helpful...it is a faith based article but the core facts are true even if you are not a believer....

1. It’s not your fault.
You could be a 20 year old with the perfect body who gave her husband all the sex he wanted, and it still wouldn’t resolve his struggle with sex addiction. Why? Because sex addiction is his way of dealing with the emptiness, pain and loneliness in his heart. Sex doesn’t resolve a wounded heart, which means anything you may do or not do sexually isn’t the cause for his problem no matter what he says. Some guys try to take advantage of their wife’s false guilt by using “if you were only giving me more sex I wouldn’t be this way” as a smoke screen. If your husband tries to use this line on you, call him on it; never allow him to pin his choice to serve the god of lust on you.
There may be friction in your marriage, but there is conflict in every marriage, and resorting to porn or an affair won’t “fix it.” If your husband is in deep, chances are he’ll be immersed in self absorption and lust, which means he may try to do anything to avoid owning up to his responsibility. 100% of the blame for his decision to worship lust lies on his shoulders, so never allow your husband to put a guilt trip on you. You didn’t cause it, and you can’t fix it.
2. Don’t allow your husband to devalue you.
Women do this when they allow their husbands to continue in sex addiction unchallenged. Before you were married if your groom-to-be had said “I’m going to masturbate to porn once a week… or have sex with prostitutes while we’re married” you wouldn’t have walked down the aisle with him – you’d have forced him to choose between you and sexual sin. Why? Because he would be treating you like trash if he said such a thing! You’re a precious daughter of God, not a trophy for his bookshelf, so don’t allow your husband to treat you like one. This means he needs to choose between you and porn, or affairs, or whatever his chosen way of acting out sexually might be.
You have to draw a line in the sand with him: “it’s me or porn... or we need to talk about separation.” He has to make a commitment to do whatever it takes, now, to break free from lust. His commitment must be shown by persistent, determined action; in this arena, words alone mean nothing. This means all porn must be removed from the house and he will no longer corrupt you or your family. If needed, a porn blocker is installed (and he gives you the password), the computer is removed, and/or all TV service is turned off. It means he goes to a group and/or meets with an accountability partner at least once every week.
Sex addiction is a hard problem to break free from, so if he isn’t going all out then he won’t get better… and if he’s isn’t going all out, chances are that he’s still playing games with lust. Lies, deception and cover up play a big part of sexual addiction, which means you can't trust that he's getting better from words alone. His actions are the clearest indicator of how serious he is about getting help, so look for proof in his deeds, not his words.

Confronting your husband may not be easy. He will be floundering in shame, and will have built a wall of isolation around his heart. Talking about his sexual sin will be a terrifying prospect to him - especially in front of you. Some men will resort to outbursts of anger or accusations to deflect attention from the real issue. If he does this, don't take the bait, and stick with the core issue. It's best that you take a few days and pray before confronting him; even better if you have friends who can pray with you.

My experience has been that women sense when their husbands are messing with sex addiction long before they understand it mentally. You have a 6th sense that we men lack, and you know by instinct when something's wrong. If your heart's telling you that something's wrong with your husband (and it's coming from the right place, meaning it's not insecurity talking) then chances are you're right. Follow your instinct up with prayer and ask the Lord what to do next.
You have every right to demand that your husband chooses between you and lust, and you should. Where women make a mistake and enable their husbands’ addiction is when they do nothing and allow their husband to continue corrupting them and their children unabated.