Is it normal to feel like something is going to go wrong with a woman's first pregnancy?

I just can't picture myself having this baby. Maybe it's because I'm only 16, 4 months pregnant, and all the odds seem to be against me statistic wise... but even though I never expected this baby, I love my little one more than anything and I don't want anything to go wrong. ): All I can do is pray. But is it normal to feel like this?