Feel like my baby isnt growing ,

Hes growing so slowly... im 21 weeks Pregnant. I have a small bump not a big bump yet. It just looks like im bloated.. i went to the doctors though and nurses measured the baby and they told me hes looking good and above average. So why arent i blowing up? Lol ....... my friend is due in October and shes already showing alot more than me and im due in September before her