Who am I ?

Being 16 and have previously battled thyroid cancer, I thought that I had seen the most treacherous course life had to offer, but that evidently wasn't the case when I was diagnosed with pulmonary edema, or as most people would call it, "water in the lungs".
This is the reason why I carry around an oxygen tank. It's hard green metal casing constantly needing to be reeled around with me, my life becoming a hunk of metal, constantly reminding me that I am a grenade, a ticking time bomb, that one day I will just be an aching memory in my parents thoughts, a grave stone, a decaying body, a nothing.
I am loved deeply but not widely, some people would call it a blessing especially given my circumstances. My doctor is always relentlessly reminding me that it will be easier on the people that love me those people only being My parents if I talk to them and tell them how I feel, I don't understand this, how can I tell them how I feel if I can't find the words to explain it to myself.
I see projecting my feelings as reminding them what a failure they have been, in keeping me healthy in keeping me alive. . I'm sure it gets hard on them sometimes knowing that the only daughter or child they will have ever had, may be dead in a matter of months.
But it's even harder knowing that they may never return to life as normal when I'm gone. Normal being before I had cancer, before medical bills, before sleepless nights, before doctor consultations, before pain, before me.