Maybe. If you arent ready and she is...?? She may just cheat on you or break up with you. You have talked with her about all this I hope. If you arent ready to be a father... which happens often first time.....Then, you arent ready. Good call on your part by the way.
I don't know what. (I do, but that can be taken many ways) Why break up with her? You really should think of this, and not ask the ask.com community. This is something you could answer better than us. But, it just means you aren't ready and she is, just give this relationship time.
If by "you know what" you mean sex... Why just break up with her? Why not simply sit her down and tell her how you feel about it, and that you're just not ready yet. She'd probably understand. Now, if she doesn't and pressures you about it and makes everything a horrible time... THEN perhaps it's a relationship that shouldn't continue. But it's all on your judgment. Good luck :)