Breastfeeding with cancer

My maternal grandmother had breast cancer at 46, paternal grandmother at 72 and mother at 56 so with a huge family history I had the gene testing when I turned 30. It came back normal for BRCA1 and BRCA2 and I was told I had just as must chance at getting breast cancer as the general population and was in no increased risked.  
So I went about living my life not giving it another thought.
Had a baby
Breast feed for 8 months
 And a few weeks after stopping breast feeding I discovered a large lump.
 I phoned breast screen Australia who told me they couldn't see me because I was under 40 and to see my GP, who reffered me to private mamograme, ultrasound and biopsies.   
Last Monday I received the devastating news that the biopsies came back grade 2, invasive ductal adnocarcinoma with metastic adnocarcinoma in my lympnodes.
My first thoughts were, omg I breast feed and had breast cancer.... what danger have I put my daughter in??  Then anger that no one warned me this could happen.
No one told me I could get BC so young. Im 36... 36?!
Was I pregnant when it first started?
Was how long had I breastfeed whilst having cancer???
My surgeon told me there is no danger to my daughter but of coarse I am still worried.

I would love to hear more under 40 stories or anyone else who found out they had cancer shortly after breast feeding or young mum worring about their young family?