Rob Eagar says, "The more you get involved in sex outside of marriage, the more the power of sex is going to diminish because you're not truly experiencing sex in the way it was designed by God. Premarital sex becomes a superficial act that objectifies another person for your selfish pleasure, and you can't have intimacy with an object. That's why sex outside of marriage will eventually become a boring, hollow experience."
This happens because you are trying to fill the emptiness in your life with something other than God. If you don't truly open yourself to God's love, then you won't be able to fill the holes. God can fulfill you, but you must let Him fill you His way, not your way. Surrender yourself fully to Him, and stop any patterns of sexual activity that you've gotten yourself into. He can help you with that as well.
"With the Lord's authority let me say this: Live no longer as the ungodly do, for they are hopelessly confused. Their closed minds are full of darkness; they are far away from the life of God because they have shut their minds and hardened their hearts against him. They don't care anymore about right and wrong, and they have given themselves over to immoral ways. Their lives are filled with all kinds of impurity and greed" (Ephesians 4:17-19 NLT).