Will you go to hell if you have sex before marriage?
We know that mortal sins keep us out of heaven. To sin mortally is to greatly offend against the law of love. Having sex before marriage is a mortal sin, if someone knows that it is wrong and freely consents to doing it. God will always love each and everyone of us. Nothing we can do will cause God to stop loving us. But if we freely choose to turn our backs on God's call to love and walk away from Him, He will respect our decision. And we will be held responsiblie for our decisions which could mean spending eternality in hell. I have heard it said that God does not send people to hell, but rather people send themselves to hell by the choice they make to turn their back on God. It greatly pains God's heart to watch His beloved children enter hell.
If we have turned our backs on God and then realize our mistake and desire His mercy, God will always eagerly embrace us back into His loving arms, if we are truly sincere. True sincerity requires that one repent and make a firm commitment to sin no more.
If someone does not ask for forgiveness, only God knows what that person's eternal destination is. We cannot judge another person or assume that certain people are in hell. We are not on that commity. We do know that not living chastly can seriously injure our relationship with God because it seriously injures ours' and others' dignity as human beings, as children of God; creatures to be loved and respected. However, by living chastly we can grow closer to Him and grow in true love of neighbor.