I am in a serious relationship with the one I want to spend the rest of my life with, but I am faced with a serious problem right now. A girl forced herself on me, became pregnant, and had a baby by me. I accepted the baby, but I can't marry the girl. It has never occurred to me to marry her. I love my fiance with whom I have done the normal thing with the family before this incident. Please advise me on what to do. The act of fornication was not intentional.
Intentional or not, when you have sex, you are responsible for your actions. "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 6:28-29). While this is talking about adultery, the same principles apply to fornication. The illustration is of a hot coal that rolls out of a fireplace. You accidentally step on it. Even if you apologize profusely to it and explain that you didn't mean to step on it, it will still burn you. Your intentions don't change its nature. The same goes for sex. Your intentions of not having sex with this girl didn't change the events that happened. As soon as you started sexually touching each other you lost any right to claim innocence in the matter. The simple fact is that sexual touching leads to sexual arousal which leads to lewd behavior which leads to sex. If you don't want to get a girl pregnant, then you have to realize that you can't start the sequence that leads to you having sex. "Now concerning the things of which you wrote to me: It is good for a man not to touch a woman" (I Corinthians 7:1).
Even though this girl seduced you, you still had the ability to say "no." There was never a need for you to have dropped your pants. "No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it" (I Corinthians 10:13). A better choice would have been to be like Joseph and run from the house (Genesis 39:5-12).
I'm glad you've accepted responsibility for your child. What you must do is tell your fiance that you committed fornication and now have a child for whom you are responsible. Because you are responsible, she will be assuming responsibility too if she marries you. She also has to decide if she wants to be married to a man who allows personal pleasure to break his commitments to God and his fiance. She might decide that she can't trust you to be faithful in marriage. She might not want to deal with a child who is not hers. But this has to be her choice. She needs to know what she is getting into if she decides to marry you.