My girlfriend and I committed fornication. I want to change our lifestyle long before, but both of us can't successfully do it. We did it for almost a year, but then we were tempted. I love her, but both of us are too weak to stay away from sex. Do I need to break up with her and start a new life, or start a pure life together? Is it possible to have no sex at all until marriage?
Is it possible to not have sex until you are married? Of course. Innumerable people before you have managed to do so. Actually, if you think about the action involved instead of your feelings at the moment, you should realize that it takes more effort to commit fornication than to not commit it. To commit fornication, you have to get each other aroused, take off clothing and engage in sex. To not have fornication, you don't have to do anything. Yet, it appears to be the other way around simply because you are allowing your instincts to control you.
For a man and woman to stay away from sex, it requires both to be committed to not tempting the other person with sex and not arousing sexual passion in the other person. More people fail because they decide they are not going to have intercourse, but they allow themselves to do everything that leads up to intercourse. Yet sex is not the final step; it is all the steps up to and including the final step. Once the path is taken the body is pre-programmed to finish. It takes great effort interrupt the natural sequence and there is where you feel you cannot control yourself.
However, the real problem is the point at which you are trying to exert control. If you want to manage your diet. You don't do it by saying "I am going to chew, but then spit out the food without swallowing." That a matter of when you are going to swallow, not if you are going to swallow. It is no different with sex. If you don't start sexually arousing each other, control isn't that hard. Once you are naked and lying on top of each other, control is nearly impossible.
What should you do? That is up to you and she. If you intend to marry her, breaking up is not going to lead to marriage. If one of you decides to give up sex, either the other will push you into sex or will leave you for not giving what they want. The only way this will work is if you are both committed to not having sex, to the point of not arousing each other and not allowing yourselves to be put into tempting situations, such as being alone with her in a house.
The easiest solution is to simply go ahead and get married. "But if they cannot exercise self-control, let them marry. For it is better to marry than to burn with passion" (I Corinthians 7:9). Yet, it is here that people have a long list of reasons why they can't marry. They excuse having sex, risking having children, but somehow the same situation doesn't allow for committing to each other for a lifetime in a covenant. People are oddly inconsistent that way.
If you have no intentions of marrying this girl, then it is best to break up. But realize this, doing so means you have been using this girl for your sexual gratification. You will be admitting that you are person who doesn't care about the person he has sex with and what you call "love" is nothing more than orgasm.