I've been wondering....

So my estimated due date was January 16 but then when they did the ultrasound they said I ovulated late and changed it to January 22 but every time I get a ultrasound the baby is measuring ahead of that.... But they won't change my due date! I'm wondering what's the chances of me going into labor on the 16th I'm suppose to have a scheduled csection between the 18th & 22nd :/