OH MY GOSH - you have really taken a huge hit! I am so sorry for your diagnoses.
Here in the twin cities of Minnesota, I go to a young breast cancer survivor support group, which is specifically for women in their 20s, 30s, and 40s. About half of us have young children... About half of us are very active to athletic... At 42, I'm in that weird transition zone between being a young adult with cancer and being old. It's very strange. There are several great programs for people who are 40 or younger... I received my diagnosis at 41. Alas....
From those two, I think you'll get connected to some great support and resources for young people struggling with cancer.
I hope this helps.