Measuring way ahead of date

Kellen • Pregnant with baby #1 after months of TTC and large weight loss. Hubby and I couldn't be more excited!
So I had my 30 week ultrasound today at 30w2d and little man is measuring at 33w3days.... She said he seems about 4lbs 11oz!
I'm freaking out! I kicked my glucose test's ass (85 with 140 being borderline) and my blood pressure is good. I have only gained 7lbs so far during pregnancy. What gives?! I'm afraid he'll get too big to deliver vaginally. 
I was 8lb 20in and my husband was 8lb 9oz and 21.5 inches.
Anyone measure this far ahead before? What was the outcome?