Our bodies are not our own. They belong to God. But being the awesome and faithful and loving God that He is, he provides for us the beautiful expression of love within a sexual relationship. He just wants us to save that for our spouse.
1 Cor 8:4,5
The wife's body does not belong to her alone but also to her husband. In the same way, the husband's body does not belong to him alone but also to his wife. Do not deprive each other except by mutual consent and for a time, so that you may devote yourselves to prayer. Then come together again so that Satan will not tempt you because of your lack of self-control.
God gives us the green light to enjoy each other and at the same time defeat the devil's plans to tempt us with another. The Song of Solomon shows us that sex is so much more satisfying when it is backed up by the love and trust and faith found in a marriage committment.
Sure, sex in and of itself is pleasurable, but that feeling is temporary. At some point, as Haze spoke of, the sexual relationship comes to an end, and then what are we left with? Most often, pain and regret.
I think we all have sexual experiences that we are not proud of. The most wonderful and incredible thing is that God wants us back. He wants our repentence. He wants us to be right with Him.
The past is ancient history. We have the freedom to live as children of God. We can't assume that because we have a romantic involvement that it will eventually turn into marriage. We can't take the position that we have to be sure we are sexually compatible with our partner before we marry. God would not put two people together and then let that be an issue. We have to trust that God has this all worked out. We have to have a marriage before we have a marriage bed.
...and don't think that typing these words is easy for me. I'm a single, 40-something, mother of two. It's going to take God's hand to send me a "rest of my life" husband. If that's not His plan for me, then I will live the rest of my life filled with the Joy of the Lord. He knows what's best.
If we put the Lord first, He will honor our wishes. He promised us the desires of our hearts. But those desires have to be in agreement with His righteous will.
It's not too late for any of us to get right with the Lord. Come as you are. That's what He says.