Please, please, please find a new doctor ASAP. That doctor is mistrustful of pregnancy and not using evidence based practices.
8.5lbs is the 75th percentile. Not every baby can be 50th percentile. And really they only start to get worried around 85-90th percentile usually.
Also generally babies are close to the size of their parents at birth, according to many doctors. I wasn't surprised my son was 8lbs 2oz. I was 8lbs 6oz and my husband was more than 9lbs. BTW I'm only 5'2". The OB in the hospital and the intern both had no concerns with the size of my son, neither does my midwife (my first was a homebirth transfer).
This doctor is bad news.
Edited add here is the CDC growth chart (for girls):
http://www.cdc.gov/nchs/data/nhanes/growthcharts/set1clinical/cj41l018.pdf
And the WHO:
http://www.who.int/childgrowth/standards/cht_wfa_girls_p_0_6.pdf
And to those that say 6-8lbs is normal. Studies show that babies weighing less than 6.5lbs are more at risk for anemia.
http://www.kellymom.com/nutrition/vitamins/iron.html
In addition, there is evidence that babies whose birth weights are less than 3000 grams - about 6.5 pounds - (whether term or premature) tend to have reduced iron stores at birth and appear to need additional iron earlier.