Sex is the greatest gift created by God. It is designed to show love between to people. The Bible tells us that in the beginning, "God created man in His own image; in the image of God He created him; male and female He created them" (Genesis 1:27, emphasis added throughout). In noting all of His creative efforts, including making us male and female, God said that it was all "very good" (verse 31). So there wasn't a design problem, and God clearly isn't against sex. However God intended sex as part of marriage. This way you learn the true beauty of sex. Click the link below to find out more.
God's Guide to Sex > The Good News : January/February 2006