Suggest Treatment For Brown Patches On The Legs

I am 9 years old ,since i was six years old I have this patches of brown things on my legs and under armpit and some on my belliy,they are growing and not dissapering they look like birthmark but bigger,my doctor say is normal that a lot of people have them,but I will like to know more about it cause they growing.Where can i find pictures so I could compare them.thanks