There is forgiveness with God, and your cry for mercy is itself a token that His Spirit is striving with you. You have done well to bring this sin into the light, for it is before Him that forgiveness is to be found, and where the offense has been, from that very place the forgiveness comes.
Hear what the word of God declares, There is forgiveness with thee, that thou mayest be feared. It does not say there is forgiveness for this sin or for that, but there is forgiveness. Where God draws no limit, do not you draw any. Though your sin has been great and has stained your conscience, there is forgiveness for you, whatever it may have been, through Jesus Christ His Son. He was sent by the Father on purpose to forgive sin, and He has been exalted to be a Prince and a Saviour to give repentance and forgiveness of sins. He has not lost His authorization to forgive.
Do as Martin Luther did when in dark distress, and say with the Creed, I believe in the forgiveness of sins, and believe in that forgiveness for yourself. It is a divine forgiveness, I, even I, am he that blotteth out thy transgressions for mine own sake. It is a surprising forgiveness, and a complete forgiveness. When you come to your great Creditor and say, I have nothing to pay with, He proclaims an absolute forgiveness of the whole debt, an oblivion to all your sin, for Christ's sake. It is not a forgiveness that He will take back, for the gifts and calling of God are without repentance. It is an eternal forgiveness, and He continues daily to forgive, for the act of forgiveness is a continuous one for those who are in Christ.
But take care that your repentance is of the right sort. There is a carnal repentance that is of the flesh, a washing and brushing of fallen nature while the heart remains unrenewed, which gives no glory to God and leads to no lasting deliverance from sin. True repentance, the repentance which is the work of the Spirit of God, gives God glory. It makes you weep and abhor your past life because of the love of Christ which has pardoned it, and it makes you avoid present sin because of the love of God who died for you. Faith and repentance are inseparable. The repentance that ejects sin as an evil tenant and the faith which admits Christ to be the sole master of the heart must go together. Ask yourself, does your repentance lead you to look out of self to Christ, and to Christ only, to save you.
You pray, heal me and take away my sin, and here is the order of grace, first forgiveness, then healing. As it was with the man sick of the palsy who lay in the presence of Jesus hoping for both, the Lord said first, Man, thy sins are forgiven thee, and afterward He made him whole. Seek first the forgiveness, and the healing will follow in its season. Forgiveness is the root, holiness is the fruit. Evangelical repentance is one of the fruits of the gospel of forgiveness and no other tree can produce it.
Therefore look to Christ alone for your cleansing, and forsake the sin which you confess. Pornography is a grievous sin against your own soul and against the holy purpose of God, who has ordained that the intimate union of the body belongs only within the lifelong covenant of marriage between one man and one woman. Do not make peace with this sin, but flee from it as from a serpent. Make no provision for it, cut off the ways of access, bring your struggle into the light with a faithful pastor or godly brother, and give yourself to the word of God and to prayer.
Let us pray for you. Father God, in the name of Jesus Christ Thy Son who died the Just for the unjust to bring us to God, have mercy upon this soul who confesses his sin. For Thine own sake blot out his transgressions, cast his sins behind Thy back, and remember them no more. Grant him true repentance that gives Thee glory, and a living faith that looks to Christ alone. Forgive him freely and fully, and then heal him. Cleanse his heart, renew his mind, and deliver him from the bondage of this sin. Set him on his feet to walk in newness of life, to love purity and to follow Thee. Let him know that there is forgiveness now, at this moment, and let that forgiveness teach him to fear Thee and to depart from evil. Amen.
Go on trusting that word, There is forgiveness, and let that blessed whisper drive away despair. You are not beyond the reach of mercy while you are yet able to seek it. Believe on the Lord Jesus Christ, and you shall be forgiven, and being forgiven, you shall be healed.