Janice,
I'm so sorry that you're going through this. My mother died when I was a teenager from cancer; she had been sick for years, but doctors could never find out why (they eventually managed to convince her she was suffering from psychological problems, and got her to spend a month at a mental hospital). She passed out one day, and after admitting her to the hospital, they found a spot on her lungs, checked further, and the cancer was everywhere, including her brain. She lived six weeks after that. She lost track of where/who she was near the end and, I know this sounds bad, but that was a blessing in many ways because she died peacefully.
You're in my thoughts,
L