Huge boobs

So, I saw a friend today that had her baby around the same time I had mine. My baby is 5 weeks and 3 days, and her baby is 4 weeks 5 days. Her boobs were absolutely huge! I mean a good 2 or 3 cup sizes bigger than before. Mine, I feel are the same size as they always were (just heavier.) To be perfectly honest, it made me second guess my supply. Is it normal to have your breasts stay the same size? Does this mean that I am producing less milk?