Measuring big

I had an ultrasound yesterday and I should be 35 weeks 5 days but measured at 38 weeks.  Miss Sara is estimated to be 7lbs 9ozs already.  This ultrasound was done to check the ventricles of her brain but they couldn't get to her head because she's so low in my pelvis already.  I ended up having a transvaginal ultrasound so they could be right at her head.  I'm a little nervous and see my doctor Thursday, thinking I might have a little one sooner than later!!  What do u guys think??  Please help, I need some insight here.  Thanks in advance!