I haven't read all the responses but here you have my 0.02, if of any use:
A friend, who is a gyno, told me that women don't get pregnant unless they wanted to get pregnant. While I know this isn't 100% certain, I wonder if your communication with her is as good as you think it is. Have you considered that she may want to get married with you and that she's trying to get pregnant to help you... err... "make up your mind"? I am not saying she's a manipulative b**ch, but Cain, you should be more aware of these kind of behaviours too.
If she is pregnant, my congratulations. :)
If not, well, maybe you should stop and think whether you are ready for this HUGE RESPONSIBILITY or not yet.
All the best