(LONG post warning lol)
Kinda scary how many are essentially saying to divorce him, which isn't allowed on this forum. Thats the problem with modern christianity in america, divorce is the easy and fast answer. But its not the right one. You can marry someone that is essentially close to Jesus when it comes to who your looking for, but it doesn't mean they will always stay like that. Many marry "perfect" people who then later end up with a new issue. inappropriate content addiction, cheating, abuse, PTSD...etc. This is why kids, especially little girls should not see movies that are "happily ever after" because it gives them false ideas on how marriage works. In real life you marry someone imperfect who has flaws. Sometimes flaws that will make you want to throw them out a window. But you don't marry them to fix them. You marry them because you love them and want to make it work. You fight for your love. You realize they may not change for the best. Or they may change for the worst.
With that said you got alot of good answers (along with some people missing their own logs in their eyes). If someone has viewed inappropriate content since they were young then its embedded in their brains. Anything can turn them to looking at it. Like if your at a beach and they see a woman whos bikini is to "small" and it may cause them to stumble. Then they may go home and look at inappropriate content because their mind has been set to "horny" mode. Yes, they should turn to their spouse, but this inappropriate content addiction isn't as easy to fix as most make it out to be. There are few that stop cold turkey. For others it can be a struggle. They may stop over months period. Years even. And even when the addiction is gone the devil doesn't say "Hmm, looks like hes not falling for my tricks anymore. Guess I'll stop now!". He will always be there waiting for a crack in the persons armor to get in. Just to make him have one corrupt thought. For my dad he said he stopped cold turkey after he married my mom. 35+ years later I've caught him on Youtube looking up sexual things. Mind you his male parts don't work anymore so he can't do anything. So it adds strain to his temptation I am sure. No sex for some people can be like telling them not to breath...ever.
Your husband needs your support. He needs to tell you when he feels an urge to look at inappropriate content. He needs to turn to you to fulfill that desire. Doing what other say like threatening him will not only put up a shield, but it will make him angry and say "Fine, if your going to get angry I am going to ignore you and look at more!". Ask him if he feels somethings lacking in your sex life that makes him turn back to the inappropriate content. Maybe you two can find out what that is and work on it so he turns to you more then inappropriate content. I can tell you I had a BAD inappropriate content addiction growing up. The allure is being able to see something different or new all the time. I will not goo into TMI because of the topic but theres so many different types of bodies, , shapes, sizes...etc. Then you get into turn ons people do (aka a fetish). inappropriate content is like any other addiction, its a blackhole that always has something to satisfy anyone who may be looking for anything. The more you corrupt your mind with it, the more you get tempted by anything you do in life. Walking down the beach as I said earlier.
My gateway to it was National Geographic. Seeing naked women from africa in it started me down my path. I was curious what breasts looked like on other women. Then I found out then got into other aspects of breasts. That morphed into curiosity about other parts of their body. So on and so on. Its true sometimes inappropriate content is a gateway to actual sexual things with other people. I don't know the stats but I'd say its 50/50 on someone going down that route. I notice though often it happens when someone is not having sex. Such as in a marriage where they are denied all the time.
Thankfully for me I trained my brain about alot of things. Like the difference between natural normal things (like a tribal woman) and non-natural things that are wrong like sex scenes in a movie. Thus I don't get tempted or turned on when I see a tribal woman. Its as natural to me as a mother breastfeeding. And when married a former inappropriate content addict needs to realize his/her sexual needs ONLY should come from their spouse. No other person. No digital person. Because you are in essence cheating on your spouse by looking at someone else. Especially if your masturbating to that something else. My wife and I have been married over two years now. She has some pain issues in her lady parts. We both have sex drives but often we don't do anything because of the pain. I don't hold it against her (though many spouses hold that sort of things against their spouse). But we both have temptations online sometimes. And we have confessed when we have done so. We always work on it. Until she can see her doctor we stay strong and are intimate when we can be.
Sadly a side affect of addiction is your honeymoon may feel boring because what you see online is way more stimulating to your brain. After the first few times he may feel like "Eh, inappropriate content online fulfills me more!". Especially as stated before because it offers variety. In his mind hes seen your body and may feel bored by it. Another side affect of inappropriate content is his expectation of what sex would be like does not match what inappropriate content showed him sex was like. The girls online are always having "perfect" sex in his mind. He doesn't realize thats not how sex is in real life. They are paid actors to have fake sex (well you know what I mean). So he needs to realize inappropriate content is a false version of sex. He needs to realize what you offer is real life when it comes to sex. And he needs to enjoy it. Of course theres nothing wrong with spicing up things of course, many couples do overtime since things can feel the same after awhile. In the end he still needs to address those things to you though. If he wants to try something new with you then let him (if your ok with it of course). Just don't do what he wants though (even if you don't like it) just to appease him. I've seen to many spouses do HORRIBLE things that they hate just to make their spouse happy.
Mmm, inappropriate content is horrible but talking to actual women about sex is worse. It could lead to other things.
Thats good. Marriage means hard work and hard times. You have to work through this battle. You need to have good communication. Pray, read your bible... go to a support group if you can. Get him into counseling if you can. I know you mentioned a phone, but if you use a computer then install this:
http://www1.k9webprotection.com/
Its made by christians. Its basically a inappropriate content filter for your internet. You can set it up so it blocks anything you want it to. Even non-inappropriate content things like drug stuff and so on. I use it and it is a great tool! Maybe get rid of his phone and buy a simple pay as you go phone. Its limiting because you can only use it for phone use, but it means he has no way to access the internet. Unless you have a computer or something. And in that case use that software I showed you.
Ah I see. Since you already use software then try the one I mentioned. You can add sites that can be blocked like "youtube.com". This way he can't access it. You can even use a password so he can't change the settings without the password. Granted it he could always uninstall it. But its worth it to try it. Frankly there will always be ways to access sex stuff online. Ads themselves can have sexual stuff. Even going to lets say gaming sites for kids, there may be people posting bad stuff in it on purpose. You could always cancel your internet. Its an extreme measure but you have to do what you have to. Maybe get rid of the computer too. Or take away the power cord or mouse...etc.
This is very concerning. Prying will cause people to put up defenses. But your between a rock and a rock right now. Ask him "If I can trust you show me your phone right now, no questions asked, no fiddling with it first!". If he says no then say "Thats why I can't trust you! If you have nothing to hide then theres no reason I can't see your phone!". Some will say its about privacy, but while that may be true, its a marriage. Your open with each other. Not 50/50. My spouse and I keep nothing from each other. We have access to our phones, facebook, emails....etc.
Next I'd tell him (for reassurance) "Listen honey, if you let me check your phone at random just for awhile and I see nothing, assuming you agree not to erase anything, the I will trust you and never look again!". Trust needs to be built back up, he needs to understand that your distrustful for a reason. If he can't even agree to that or just continues to look and be angry then the next step is counseling, by a christian. And of course pray, pray and pray!