Is it normal to have stretch marks covering the boobs?

Well I know most people get a few stretch marks, but I have them completely covering my boobs, they are faded and shrunk and not heaps noticable, but you can still see them and they go all around my boobs on every bit of skin, why do I have so many?? I never seen anyone with as many as me..My boobs arent that big, only a C-D depends on the brand..