This sometimes happens. Is it possible that the doc set your due date wrong ? My sister used to teach lamaze and doctors were forever changing due dates, and then she'd get mad at them cuz they would have to have people start lamaze early, and --oopsie -- the original due date was the right one !
But that is one possibility. I've also seen people told they were going to have 9 lb babies, and come to find out, the baby is right on schedule and is 6 or 7 pounds. ?? Medicine is not an exact science by any stretch of the imagination, and they do tons of tests these days to avoid malpractice suits, and they scare pregnant moms to death in the process.
My bias stated . . . :-) I will also tell you that my kids have ranged in sizes -- My first was 8 pounds, the second was 9, third was 7 and I can't remember the size of the 4th. (shame on me) The 9 pounder was my easiest delivery. She was LONG, but not big width wise, and her head wasn't big.
Try not to worry. It's hard, because you love your child, and you want so much for this to be a happy time, and you want your child to be born safely and healthy. One day at a time. If the baby is too big to get out, or breach or labor doesn't progress, yes, they will do a C-section, but most babies come through the natural way, and they do very well. (as does mom)