Boys an size?!

Ashlee

So my son is going on 5 months an he seems to be a normal sized baby but most the clothes he wear has to be a bigger Month size is that normal? I like giving him a little room to grow but he can fit 9 months onesies almost perfectly he is 16 pounds so he is not overweight but he does seem solid an a little chunky please if anyone can tell me if he is supposed to wear bigger clothes?