So this is the first time this has happened but this light brown discharge is coming out of my breast its very thin, but is it cancer or is it normal?

No one but a doctor could diagnose cancer, honey. Go see one. :( Sounds to me like an infection of some sort.

So this is the first time this has happened but this light brown discharge is coming out of my breast its very thin, but is it cancer or is it normal?
I'm only 14 though isn't it like really rare?

Infections are not rare, cancer is rather rare. Please talk to your mom and go to the doctor, infections can be very dangerous, and cancer is obviously bad, although I doubt that you have cancer, very much.