Premarital Sex is defiantly a sin. Remove yourself from any situation that makes this sin more tempting to happen, ie living together, being together alone, ect, etc. What you need to do is repent first of all. Everything that you do needs to glorify God. Even this relationship. If you aren't honoring God in this, then He will not bless the relationship because you are, in essence, making the relationship an idol, putting it before God.
That being said, reflect upon yourself and make sure that what you aren't doing is trying to get your emotional fixes solely from her. Because we are created to first have a right relationship with God. Once we know His love and have a relationship with Him, all other relationships are more fulfilling because we are first fulfilled by God. Human relationships were never meant to satisfy the deep longing within us for connection with something greater than ourselves.
Thirdly, love is not an emotion. It is a decision. It is an action. You choose every moment to love. In an argument, you may not FEEL love. But you act out love by fighting fairly and choosing not to put the person down. By choosing to be committed. Life will bring so many obstacles your way that will challenge your relationship. But you have to be willing to fight to keep our relationship. Whatever the challenges may be. It has to be worth it to you. Cherish it.
Fourthly, PRAY! Pray for God's guidance in this. Marriage is not something to be entered into lightly because you will be with this person for the rest of your life. [Assuming, this relationship will lead to marriage.] Once you are married, even if perhaps that is not the person that God had intended for you, it certainly is now. Not that we can thwart God's will or plan for our lives.
