Is it a sin for my girlfriend to give me a handjob and for me to finger her? We've already done both, and I'm starting to feel kind of guilty over it. I don't know if it's considered 'sin' or not because it isn't sexual intercourse. We're both Christians too, and we're just blinded by the fact that it isn't actual intercourse, but we're still touching each other's genitals. I'm so confused about this, and we're looking for help.
Your guilt is a hint that deep down you realize that what you did was wrong, even if you can't put a name to it. Sin doesn't start when you put your penis into her vagina. This was a point Jesus made during the sermon on the mount. "You have heard that it was said to those of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:27-28). The Jews in Jesus' day had narrowed the law down to the physical act of adultery, but Jesus pointed out that adultery starts when a man looks at a woman with lustful thoughts. "And He said, "What comes out of a man, that defiles a man. For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, thefts, covetousness, wickedness, deceit, lewdness, an evil eye, blasphemy, pride, foolishness. All these evil things come from within and defile a man"" (Mark 7:20-23). While you were fingering her and she was rubbing your penis, I'm certain your mind was not tomorrow's dinner plans. Likely you were wanting to go much further, but the fear of actually committing fornication restrained you; yet, in your minds you were involved in lust. "Let us walk properly, as in the day, not in revelry and drunkenness, not in lewdness and lust, not in strife and envy. But put on the Lord Jesus Christ, and make no provision for the flesh, to fulfill its lusts" (Romans 13:13-14).
I assume it went to the point of you ejaculating. People often seek out alternative ways to have sex, such as hand jobs or oral sex, in an attempt to have sexual gratification without the risk of sexually transmitted diseases or pregnancy. The problem is that diseases can still be transferred through the skin-to-skin contact of a hand job or fingering. True, the diseases will not be spread as easily, but it is not a preventative method. Nor, surprisingly, is it a guarantee that pregnancy will not occur. When you ejaculate, then there is always a possibility that some of your semen might be moved to her vagina either accidentally or purposely. Sperm swim regardless of the method used to get it to the appropriate place.
The problem with sexual touching is that it naturally leads up to sexual intercourse. Though not your intention, people don't think well when they are sexually aroused. To claim it won't happen to you is foolishness. It is a part of the deceptiveness of sin. You think that because nothing more than a little sexual pleasure occurred, then it is not so bad. But eventually the novelty wears off so you try a few other things which aren't that much different. You tell yourself that it isn't that bad that since you didn't have your penis in her. Gradually you go further and you're arguing that so long as you don't actually ejaculate in her, it isn't so bad having your penis in her for just a short while. Step by step your resistance to sin is worn down. That is why Solomon said concerning adultery, "Can a man take fire to his bosom, and his clothes not be burned? Can one walk on hot coals, and his feet not be seared? So is he who goes in to his neighbor's wife; whoever touches her shall not be innocent" (Proverbs 6:27-29). Even though it just started with touching, Solomon said a man cannot pretend innocence. Just as you know that hugging a burning coal is going to burn you, everyone knows that sexual touching is going to eventually lead to sex. And when it does happen, your argument that "I didn't mean to" will be simply foolishness.
Besides all of this, God said that men and women are not to touch each other sexually before marriage. "Now concerning the things of which you wrote to me: It is good for a man not to touch a woman. Nevertheless, because of sexual immorality, let each man have his own wife, and let each woman have her own husband." (I Corinthians 7:1-2). Paul is not talking about holding hands. He is stating that men and women ought not to sexually touch each other outside of marriage. Sex and the things that lead up to sexual intercourse only belong within a marriage.
Now just for a moment, imagine that you two were married. Would you except another man having his fingers in your wife or would she accept another woman having her hands on your penis? Even if they say, "But we didn't have intercourse"? Of course not. So why are you making excuses for yourselves now? You two are not married. There is no guarantee that you will marry, even though you might have intentions in that direction. Until you and she say "I do" in a wedding ceremony, you have no business touching or looking at the private areas of a person who just might end up being someone else's husband or wife.
I trust that by now you are no longer confused about the matter. You've both sinned and you need to straighten yourselves out with God.