The Bible does address the issue of unclean thoughts. For example Messiah told people that if they even lusted after a woman in thier hearts, then they had committed adultery. We are also told to "Bring every thought captive" to Him.
Since you do not seem to know these things, I'm guessing that one part of the solution to your problem is to study the Bible very intensively. We're supposed to do that anyway. It brings so many blessings.
Your story is very familiar, so many have experienced the exact same addiction and progression. You're certainly not alone. You might want to check out the Every Man's Battle site, and/or book. Perhaps you can get some insight and/or support. One of the things they teach is that you have to so carefully screen what kind of entertainment you put before your eyes.
"Anyone who continues to sin becomes a slave to sin" is also in the Bible.
You are wasting your time trying to "Just say No", therefore. "Without Me you can do nothing." The one and only cure for a problem that has become a big "stronghold" is the Stronghold Breaker, Messiah.
Your answer will be in your prayers, and hopefully with some fasting - maybe a 24 water fast once a week, not too strenuous as fasting can damage your adrenals.
Do not expect that you will say one prayer and Boom you are "fixed." That could happen if you really pray in a deeply humble way. Btw desperation is goooood! It's so humble and Abba loves humility. "Humble yourself in the sight of YHWH [aka the Lord] and He will lift you up."
And really, you'd be surprised to know that it may not be the porno that is the biggest problem in His eyes. The biggest problem for us all is a general heart of rebellion and the sin is just the symptom. My suggestion, since you asked, is not to pray first to be freed from that particular sin. Pray for a heart filled with humility. Pray for faith that what He has to offer you is infinitely better than whatever you have been looking at.
Pray for healing of anything in your past that has led to you wanting that kind of stimulus. I have no idea, but you may have some kind of pain that it distracts you from, maybe from the past. Whatever. So often - again I have no idea about you - people have been messed with as kids and that can lead to pornography too.
Ask for forgiveness. Later, after all that, ask for healing from the porno. And oh yeal, even before the prayers, praise a lot. "YHWH inhabits the praise of His people..." and where he is the devil (who is behind all the porno) cannot be.
I also think we should say, not mechanically but reflectively, the Lord's Prayer every day. After all it says, "Give us this day our daily bread."
We are told to praise far more than we are told to pray. "Come into My gates with thanksgiving and into my courts with praise." Praise first & most. Don't know what to praise for? Look around you. You obviously have a computer and an education 'cause you can type. You have food, shelter. The list of things to praise for will never be exhausted. Also you can go to sites that list Bible promises and praise with them. "Thank You Abba that you say 'Sin shall have no dominion over me...Thank You that Messiah died that unimaginably horrific death on the cross for me so that I could be freed and forgiven..." Stuff like that.
It takes time to get freed because it takes time for us to humble ourselves enough before the Almighty. We are so resistant and prideful, more than we even admit to ourselves.
Abba doesn't just want you free from porno. He wants you focused on Him. How often? Around the clock. It may seem like a burden, but as He leads you, it's really freedom that brings so many blessings and protection. "He who keeps His mind stayed on me will be kept in perfect peace." Only He can give you the strength and persistence in doing that, and only prayer can get His help.
It's not just porno that is "Every Man's Battle", it's life that is everyone's battle. Life will be a battle til the day you die in one way or another. Your best defenses, your best weapons are praise and prayer and fasting. But through them you will be refined and made ready for Heaven.
My personal experience has been that if we are being strongly tempted, we haven't prayed well enough. If Messiah is in the battle, the temptations, if any, are small & easy to handle. If He isn't we lose sooner or later, usually pretty soon.
When you do get deliverance, you have to hang onto it the same way you got it! See the parable of the man who had one demon, got his house cleaned up, fell into temptation again and then got 7 demons. See the story of the man Messiah healed who was told, "Go and sin no more lest a worst thing come upon you." (Not that, if you do fall again, He won't be there to help you, it's just that your problem may be even worse thereafter.)
You have every reason to be hopeful! Countless people have gotten free from countless sins through Messiah's help, and that certainly includes me.
Praying for your freedom....
