You cannot have sex before marriage and be a Christian at the same time.
Virginity is holy and normal for real Christians. It also leads to health.
As merciful as God may be, it is a disqualifying factor that demands a repentance so great so as to deem it unforgivable to most.
This sin requires a conversion of gigantic proportions to acquire the mercy needed: such as telling everyone your sins, becoming a global missionary, submitting to hours and hours of prayer for weeks and months, occupying the place of humility and debasement.
Even St. Augustine, spending the rest of his life writing, gave publicly his confessions and volume upon volume upon volume of theology to repent of the sins of his mind and body.
May whoever disagrees expect the fires of hell as his rightful place, for whosoever believes contrary to this and regarded as a Christian contradicts the multitude of repeated commandments in Scripture that say, Do not be deceived, the sexually immoral, the unrighteous, shall not enter the kingdom of heaven.
Be chaste, do not trouble the Lord or his people, or count yourself a nonbeliever and leave his flock.