Why is randomness in suffering?

I am a young mother suffering from terminal cancer, would leave my children motherless, that breaks my heart. I am truthful here, in my present life I have been righteous, I have never consciously hurt any human or animal except provoked. In fact my children say to me all the time I am the best mother they could ever have. I wonder for those people who believe in God ( I want to believe as well) why would not God let me stay alive to fulfill my lifes dreams. Why am being dragged away from life against my will. I have to do so much. The other possibility is that terrible things happening to people is just bad luck. Why me? Why not me as my children need me. The questions are so many...I am grappling in the dark for answers. I just hope that light will enter my my soul and give me the answers. My love for my children is no powerful that all the religious explanation like karma, gods trials, suffering is part of life does not make sense. The murderers live until ripe old age enjoying the state benefits then a working mum like me is asking for life of giving. Why taketh away from me?