Firstly Annie, Welcome.
Secondly - take a breat (I know that is hard, but it is needed)
I KNOW it is hard and scary, especially as you watched your Mum go through it (I also watched my Mum go through breast cancer, and lymphatic cancer (unrelated to each other) so can sympathise fully). Just because your Mum lost her battle does NOT mean you will, treatments change all the time, and no 2 breast cancers are the same (stage, grade, type, receptor status etc)
If you, your husband or extended family need help dealing with this then you can get help from organisations like the Cancer Council, Breast Care Nurses your local hospital etc.
Where abouts in the world are you? AS there are lots of face to face support groups ot these as well, for people, young women, those with BRCA genes or strong family histories, or set states and diagnoses etc etc.
Your thoughts are NOT silly they are understandable and NORMAL, we all go through the why me, why now, why why stage and the I dont want to die etc that is totoally normal. The waiting is the worst, it plays games with your mind and emotions as you think of all the what if's etc.
Another thing - this is NOT something you have or are to putting my family through, this is NOT something you asked for, this is NOT something you wanted, this is something that has happened to you, and you are not making life difficult for your family, you are coping with a new diagnosis.
Your Brothers, husband, Nanna's and other family members will cope, it is VERY hard having to tell them especially as they watched your Mum go through it (I know it was hard for me to tell my family and to tell my sister that she is now at even much higher risk of getting breast cancer herself (and I was diagnosed 3 days before Christmas i didn't want to ruin there Christmases so waited until afterwards to tell my brother, sister, stepdad, and other family members about my diagnosis, making sure I enforced the fact that I had EARLY breast cancer and while I would need a mastectomy and maybe further treatment, it was early and survivable.
I am also being sent to see the medical genetics clinic on 01/08 to see if I qualify for the free BRCA genetic testing to see if I carry the breast (and ovarian) cancer gene (as this will also effect my little sister, and older brother their kids etc), and will determine if I have surgery to remove my ovaries when I have my other breast off (I decided when I was diagnosed that I didn't want either of my boobs and my breast surgeron agreed to do 2 mastectomy and reconstructions but I only have the chance to do the cancer side quixkly and the other side is being done at the end of next year or early 2013, as a preventative surgery)..
Have a look at some of the posts/ blogs on the site, read through them ask questions, everyone is willing to tell you what ever you want to know and to help out in wany way they can.
There are a couple of blogs here that you might find helpful with your new diagnosis, your upcoming journey and your upcoming hospital stay.
Have a look at:
Hope this helps a little