The Bible is unequivocal in its condemnation of intimacy before marriage, while encouraging abstinence. It is important to note that there is a strong correlation between these two concepts. The Bible is very clear that there should be no sexual relations before marriage, and there are no exceptions to this rule. Even if a couple is engaged, it is still considered a sin for them to engage in premarital sex.
The Bible does not condone nor tolerate any form of sexual activity prior to marriage. If a couple does not abide by this rule, they will face the wrath of God and no one will be exempt from guilt if they engage in sexual intercourse before they are legally united in marriage. This is God's intention and it is one of the most serious sins that can be committed when even a committed partner has sexual relations before marriage. The Song of Songs is perhaps the best book in the Bible that speaks to the joys of sex, as it reminds us that sex should only be enjoyed within the confines of marriage.
Simply having sex or living together does not fulfill the requirements of the biblical model of marriage. In due time, it will reward you with a more complete, beautiful and fulfilling experience because you have respected it enough not to use it in an immoral and unbiblical way.