I haven't been focused too much on why this happened to me. Deal with it first, then deal with the why, is how I'm feeling these days. But we, as a society, need to be interested in why so many women get breast cancer. Cures, treatments, aren't enough: we need to prevent it in the first place.
So here are some things I've found on "the why":
State of the Evidence 2008: The Connection Between Breast Cancer and the Environment
Breast Cancer and the Environment from the Silent Spring Institute
Mass. Breast Cancer Coalition's Science and Research Links
Causes, Prevention, and Environmental Links from Breast Cancer Action
Dr. Susan Love Research Foundation (not really about "the why" but she is just so amazing...)