My wife just told me she has the Big C,im in bits?

Hi look i know it is not manly to come to a site and open your heart but i have no one else to turn to right now,My wife and i are married 10 years and it has been the best 10 years of my life and i couldn't imagine my life with anyone else,so far we have four beautiful children from 9 years old all the way down to 9 months.I love my wife and kids and we all have had an amazing life together.Four days ago it was at just the strangest night we put the kids to bed and had an hour to ourselves she then just came it and said she wanted to be honest with me i thought she did sum ting bad but then she said she had breast cancer and its like my our whole life tumbled,i can't understand how shes staying so calm she said she wants us to carry on as normal im the only one who knows and she wont tell anyone and warned me not to tell anyone ,im scared frightened and can't stop thinking something will happen to her ,I find it hard because she dosent want to talk about it she says she will be fine and to concentrate more on the kids i cant!! if i lose her im nothing i know i can't stop cancer but i have never been more scared in my life !!my sister died of cancer but it was in the stomach ,i can't sleep i spend my night lying there just looking at her thinking she has something that could part us,what do i do i can't cope i can't eat i've no interest in anything anymore she tells me not to worry my late sister told me that what do i do!!!