Your honest confession is heard, and the very distress you feel about this struggle is itself a sign that the Spirit has not left you to be hardened in sin. The burden you carry is heavy, for every temptation that comes from Satan is also a trial from the Lord, and in that trial your faith and steadfastness are being proved.
Scripture gives us the true pedigree of sin, that when lust has conceived, it brings forth sin, and sin, when it is finished, brings forth death. Any sin, whatever it is, if we cling to it and love it, will bring forth death, rest assured of that. For this reason purity and charity are the two great garments of Christianity, and charity without purity will be of no use. We may do many good things, yet without holiness no man shall see the Lord. To hate the lust while it tempts you is not sin, for a man may be tempted and yet hate the temptation and there is no sin in it to him. The sin lies in conceiving it, in welcoming it, in giving it place until it brings forth its bitter fruit.
You say that when you try to stand, something bad happens and you give in, and now you feel drawn to take it further against your own desire. That is the peril of temptation itself, and it is right for the Christian to pray, Lead us not into temptation. The prayer does not mean that we will never be tried, but it asks, spare me from too great trials lest I fall by their overcoming my patience, my faith, or my steadfastness. Oh, save me from the mischief of the temptation. Let me not stain my garments. Let me not slip nor slide, but may I stand fast at the end of the day.
Hear this warning with love, never go into temptation. The man who prays Lead us not into temptation and then goes into it is a liar before God. If you know the place, the image, the hour, the conversation, the screen that kindles this lust, you must not go there. Flee it as you would flee a fire. God at times leads us into temptation by the withdrawal of Divine Grace to show us our weakness, and by His providence placing us where we are severely tried, but we must not for any reason desire to be tried, nor put ourselves in the way of it.
Your hope is not in your own resolve, though resolve is needed, but in looking to the Lord Jesus Christ for all things. To the world Christ is one who lived long ago and died, but to us He is alive, He is our familiar Friend. Saints first learn the art of overcoming evil, and then they learn the way to overcome goodness itself, and there is nothing to be done but just to look to Him. Give Him that overcoming glance of faith, looking to Him to keep you, to cleanse you, to be your strength in the moment of assault. He is mighty to save and mighty to keep.
Turn to Him now in repentance and faith, for salvation is through Jesus Christ alone, and His blood cleanses from all sin. Confess the lust as sin, not as a sickness only, and ask for His forgiveness and His power to walk in purity, for purity belongs within the lifelong covenant of marriage between one man and one woman, and all sexual desire outside of it is to be mortified and denied.
Pray daily, Lead us not into temptation, and watch as well as pray. Put away the provision for the flesh. Seek a faithful brother or pastor to walk with you in accountability, bring your struggle into the light, and fill your mind with that which is good, overcoming evil with good. When the temptation presses, cry at once to Christ, look to Him, and long for His appearing and His help in that very hour.
May the Lord keep you, restore to you the joy of His salvation, and teach your feet to stand fast. We will pray that He will not leave you in temptation, that He will supply grace to flee from it, and that He will make you pure in heart, that you may see God.