Dont worry. My girl was smaller than average too. So my doctor told me to have 8 to 10 egg white per day. I did that for the last 4 months and she was born at week 37th, weighted 6 lbs only. Nurses said she is a smaill size baby needed to be feed every 3 hours (norma is every 4 hours).
And she is now 4 months. almost 17lbs. wearing 9-12 months old clothes.
To me.. it's all about gene. Her father is about 6 ft. (I am only 5). She got it from her dad!