Sex before marriage is sin.

The Divine Institution of Marriage; that it is a Sacred Covenant between a man and a woman (Gen. 2:24; Matt.19:5; Mk.10:7), who as Husband and Wife commit to live in a monogamous relationship for love, procreation and companionship (Prov. 5:18-19; Mal. 2:15; 1 Cor. 7:3-5), until death (Matt. 19:5-6; Mal. 2:14-16; Ro. 7:1-3; 1 Cor. 7:39).

Hebrews 13:4. Marriage is honorable among all, and the bed undefiled; but FORNICATORS and ADULTERERS God will judge.

1 Corinthians 6:9-10. 9 Do you not know that the unrighteous will NOT inherit the kingdom of God? Do not be deceived. Neither FORNICATORS, nor idolaters, nor ADULTERERS, nor homosexuals, nor sodomites, 10 nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners will inherit the kingdom of God.

Galatians 5:19-21. 19 Now the works of the flesh are evident, which are: ADULTERY, FORNICATION, UNCLEANNESS, lewdness, 20 idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, 21 envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will NOT inherit the kingdom of God. —Sex outside marriage is the sin of fornication. Masturbation, pornography, anal and oral sex is the sin of uncleanness.

Sin is not forgiven until you repent of it (ask God for forgiveness for it in Jesus name 1 John 1:9) and stop continuing in the sin. Proverbs 28:13 He who covers his sins will not prosper, But whoever CONFESSES AND FORSAKES THEM will have mercy.

Sex is a gift that God only allows within a Marriage between a man and woman.

Hope this helps someone. All glory to Jesus alone.