Don't worry about it too much honey.
If bub is too big docs will usually want to give you a CS. But just remember if you don't want a CS, my great grandmother gave birth to a 13.7Pound baby with no tearing! (yeah i know, wonderwoman eh) And he was her first. Her next four kids were big as well, with the last one being a healthy 9.9pounder.
My little boy is coming out on 30th of July via CS, he's projected to be around the 10-12Pound mark.
But the docs gave me a choice, i could either be indiced at 35 weeks and go naturally, or leave him to bake a bit longer and have him out at 39+1 via CS.

If your freaking out, talk to your doc or midwife about it and figure out what YOU want to do. If you tell them your scared, they'll try to help you relax a little.
Good Luck!!!