You had sexual intercourse. With sexual intercourse there was always a risk of her getting pregnant. I'm sure you knew this.
You can express your concerns to her, of course, but you've created a life. And you have to face the responsibility that has been thrust onto you. Either you stay with her, and try to make the best out of your situation and raise this child with this woman that you are crazy about, or to run away, leave her and pay from afar.
Yeah, it's scary. And yeah, it's going to change your life. But think about it. You're going to be a dad.

Is that not in itself a wonderful thing, regardless of whether you think you have the financial stability to raise your child in the exact way you wanted?
While I do agree that it should be a joint decision - women as the carrier of the child seem to be given a special power to decide ('cause it's inside them) - so there's not much you can do if she decides she wants to keep it (which really does make you wonder about feminism, and how they're treated as "lesser" ¬_¬ but that's beside the point, lol) what you have to decide is whether you want to play an active role in this child's life.