What can i do?

Ive published a couple ads on this site. Today im feeling in the mood to write. Just a brief story about my personal life . Well let me begin by introducing myself. i am a few days shy of 28. i come from a broken home.I have had a rough life . I used to play soccer when i was 9 years old.i was pretty damn good at it to.until one day my dreams of one day becoming a proffessional soccer player were shattered .i witnessed a brutal homicide.A gang member was shot to death while i kicked my ball up against the side wall of a gymnasium located on the park. i was nine years old and did not have the tools to cope with such traumatic event. That incident killed my passion for the sport. Ever since that day i have lived in fear. it changed my life . As i grew older my life took a turn for the worst. i dont blame anybody for the poor decisions i took. But the decisions i made took me to a dark and lonely place that not many have visited. I found my solution then.ALCOHOL. And with alcohol came stronger substances.I got involved with drugs and alcohol. It damn near took my life plenty of times. I wanted out but my addiction had a hold of me.I didnt know how. Fast forward some years , I was homeless , hungry , desperate and willing to do anything it took to get out the hole i was in. For those whom are having a hard time believing their is a god, well let me tell you think again. i have experienced a major transformation. i was introduced to a twelve step program. im not ashamed of putting it out there because thats who i am. i have been sober for over a year now. i was diagnosed with unresolved PTSD because of the incident i witnessed when i was 9. Early in sobriety i was told that i had to build a solid foundation before anything. I didnt understand what a foundation was. Up until my younger sister was diagnosed with stage three colon cancer. It broke my heart. I looked to my siblings for support , but how can i get support from them when both of my siblings are serving life terms in prison, my mother is deep in her meth addiction and my father is nowhere to be found? where can i look? is this the foundation they spoke about so much? well it sure is. a year and a half ago i was homeless , with nothing . living in the street , and going days without eating nor sleeping.Now i have a bed that belongs to me and a roof over my head that i pay for with my hard earned money.their is one thing that is killing me deep inside. I spoke to the my sisters doctor. he told me the severety of my sisters condition front to back. he told me all the details and provided me with information no one knows. my sister does not know that she has stage three cancer . all she knows is that she has a disease and she has to be strong. thats what was told to her by the doctor. Now my whole dilema is this. i dont know if i should tell my sister the true nature of her condition or if i should keep that to myself . This is not an attempt to create pity for me . i have never been through this type of situation before and honestly i have no one else to ask for advice. literally. I am sure someone out there has had a family member that has/had cancer . I am powerless.and if i am powerless, the real question is .What can i do?