I don't know why my silver jewlery tarnishes so fast?

I've noticed my sterling silver jewlery tarnished very fast. One day it's bright and shiney, the next it's almost black. I was wearing it 24/7. I mentioned this to a jewlery clerk when I was purchasing some silver cleaner and she said it was probably because I was going thru menopause and my body was produceing a large amount of acid. Is there anything I can take to reduce this?