We understand your struggle and commend you for reaching out and recognizing the sin that has been entangling you. It's important to acknowledge that sexual immorality, including masturbation and lust, is indeed sinful and can open doors to demonic influences. As it is written in Ephesians 4:27 WEB, "Give no place to the devil."
Firstly, we need to emphasize the power of the name of Jesus Christ. It is only through His name that we can be saved and set free from sin and demonic influences. As it is written in Acts 4:12 WEB, "There is salvation in none other, for neither is there any other name under heaven, that is given among men, by which we must be saved." It's crucial to continue calling upon His name and to believe in Him for your deliverance.
We must also address the issue of ongoing sin. While you mentioned that you have repented, the fact that you continue to give in to temptation indicates that there is still a stronghold in your life. As it is written in Romans 6:1-2 WEB, "What shall we say then? Shall we continue in sin, that grace may abound? May it never be!" We must take sin seriously and strive to live in holiness.
To overcome this struggle, we recommend a few things. First, remove any triggers or temptations from your life. This might mean giving up certain video games or movies that fuel your lust. As Jesus said in Matthew 5:29 WEB, "If your right eye causes you to stumble, pluck it out and throw it away from you. For it is more profitable for you that one of your members should perish, than for your whole body to be cast into Gehenna."
Second, put on the full armor of God each day. As it is written in Ephesians 6:11 WEB, "Put on the whole armor of God, that you may be able to stand against the wiles of the devil." This includes the belt of truth, the breastplate of righteousness, the shoes of the preparation of the Good News of peace, the shield of faith, the helmet of salvation, and the sword of the Spirit, which is the word of God.
Let us pray for you:
"Father, we come before You in the mighty name of Jesus Christ, lifting up our brother. We thank You for the conviction of sin that he has experienced, and we ask that You grant him complete deliverance from this struggle. Help him to fully repent and turn away from this sin, and give him the strength to resist temptation. Equip him with Your full armor, Lord, and help him to stand firm against the schemes of the devil. In Jesus' name, we pray. Amen."
Continue to seek God, read His Word, and pray. Remember, God is faithful and will provide a way out of temptation. As it is written in 1 Corinthians 10:13 WEB, "No temptation has taken you except what is common to man. God is faithful, who will not allow you to be tempted above what you are able, but will with the temptation also make the way of escape, that you may be able to endure it."
Stand firm in the faith, and keep resisting the devil. As it is written in James 4:7 WEB, "Be subject therefore to God. Resist the devil, and he will flee from you." Trust in the Lord, and He will set you free.