Your honest confession before the Lord is precious and He hears it. The message of the Bible to anyone who has sinned is that there is forgiveness with God. You have not gone too far. God will forgive you and God will heal you and change your life when you turn to Him.
Scripture shows that God offers both forgiveness and healing and restoration. He promises to restore comfort and to give peace. Isaiah speaks of the Lord bearing our griefs and infirmities, and Matthew shows that Jesus fulfilled that not only in forgiving sin but in healing sickness and brokenness. When you bring your sin to Jesus and receive His pardon, you receive the greatest miracle of all, the forgiveness of your sins and salvation. That miracle is greater than any physical healing, and it brings a peace that ends the war within. Before that peace comes, the heart without God is like a storm tossed sea that cannot rest. When you give your life to Jesus and receive His forgiveness, the conflict is over and He gives a wonderful and lasting peace.
Pornography is not a small thing. It has a power to take a person captive and hold him like a slave. Like addiction to alcohol or drugs, it can grip the mind and emotions and grow progressively stronger, drawing a person to want more and leading into every form of sex outside the covenant of marriage between one man and one woman, which Scripture calls impure. Many homes and marriages have been broken by it, and it is part of the moral decay that surrounds us. You are right to see it as sin and to want to be free.
Take comfort in the story of Manasseh, a man who went further from God than most of us could imagine, yet when he prayed and turned to the Lord, he found that God is loving and forgiving. If God forgave him, He will surely forgive you when you repent and ask Him.
Healing from this kind of bondage often is not a circus or a superstition, and it is not always instant. Jesus healed in many different ways, sometimes with a touch, sometimes with a word, sometimes at a distance, and once through a gradual process. That reminds us that God is not confined to one pattern. There is a divine process of healing that God has built into our bodies and minds, and He also heals the wounds and scars in our emotions and memories. Believe strongly that God does heal, but also understand that healing can be gradual, and the inner healing of the mind and heart is real and divine even as you continue to walk it out day by day.
Your only power against this is prayer and a full surrender to Jesus Christ. Come to Him in repentance, ask for His forgiveness and cleansing, and ask Him to do that healing work in you. Do not carry this on your conscience as if it must haunt you. The only thing that keeps you from forgiveness is not coming to ask for it. When you come, He cleanses.
God desires purity in His people because purity brings power and health to the whole life. Even a little impurity can affect the whole person, so He calls those who belong to Him to maintain a standard different from the world and to walk in holiness. This means turning away from pornography completely, guarding your eyes and heart, and pursuing what is pure.
God is extending His peace and healing to you today. Keep praying, keep turning to Jesus, and trust Him for both the forgiveness you have asked for and the daily healing that will make you whole.