Calcification on teeth

I'm 18 and already have calcification on my teeth. Idk why, because I've always made sure to take good care of my teeth. Do I have some sort of deficiency? I'm embarrassed to smile in pictures. It started when I got braces, and I didn't really notice it until I got my braces off a year later. The dentist said she could use a technique called binding but it's expensive. Could a whitening toothpaste help decrease the difference maybe?