Is it possible for a girls to shrink?

I am 15 and i have been soo afraid of diseases, swine flu and cancer lately. I have ocd, and once i read that could get dramaticly smaller or bigger, i have been freaking out about my s seemingly getting smaller. I dont know if its just fear, or if my are really shrinking. I am scared, and i dont know how dangerous that is .my bra still fits so mabey... Thanks.