If This Is It, Please Let Me Know

Not only is just daily living and survival hard, but so is a lot in my life. It's crazy, I always answer, "I'm great. I'm fine!" when someone asks how are you. Because you know what, compared to a lot of other people. I have a home, I have clothes, I have a family, my parents are together (married for 18 years, together for 26), everyone is in good health, etc. I am so thankful for all of it and couldn't imagine any of it being taken away from me. I don't ever want to have to be in comparison with someone and say, "...Well I got it worse than you do. My life is miserable." No, that's not cool and I don't want to argue with someone over who has the worst going for them. Even though my life is going better than those who have no home, no family, can't find a reason/purpose for living--I feel like the past couple of months my life has just been sinking lower and lower than I thought it could.
On August 22nd, I was planning on going out. It was the Friday of the week I had just got back from my family vacation, my dad was on his way to work and my mom was already at work. It was about 2:40pm or so, when I got a phone call from my mom's job saying she had an accident and was in the hospital. I don't really want to get to deep into it, but ultimately we found out my mother has growing a tumor in her head, but she's still here and I'm thankful for that. My dad, although we haven't been the best of friends since I hit about 13, he's still my dad and I love him. He goes through a daily fight trying to stay healthy. He has high blood pressure, high cholesterol, he isn't allowed to eat over HALF the things that I'd QUICKLY inhale in a second, he has a chronic back pains that sometimes causes him to be paralyze over a short amount of time, but yet he's still here, still fighting, working hard day-to-day to make sure my mom and I have this beautiful house to live in. It's hard seeing my parents like this only because I'm not in a financial position to help them and I "make" them (unintentionally) help me by paying for the food in my belly, my bed to sleep in, my car I drive, etc. This is one of the BIG reasons I decided not to go to UMD-CP anymore, I couldn't possibly put my mom through it for another year. Now I don't want you guys thinking my family is dead BROKE, but I'm just saying my parents have worked hard to get this far.
Well the biggest bomb has just hit me yet. Today I find out my sister has breast cancer. She's only 28. Not married, no kids. Worst of all, her mother died from cervical cancer. (We have different moms, but same dad). She's young and still in school and she has to deal with this. Worst of all, alone. You see, my dad excommunicated her from the family because she ran away from home when she was MUCH younger. Since then he's refused her and doesn't keep contact with her at all. But my mom looks at her as if she's her own daughter, Calls everyday, sends her money, the whole kit-kabootle (sp). Oh, I know I already said worst of all, but this is REALLY it, my sister has chosen not to continue visiting the doctor and receiving any treatment.
So I'm feeling down, is this life? Is this really it? Is this what the TV, movies, books/stories are all portraying? Is this normal? If this is it, please let me know. Cause I don't know how to react, I don't know how to give it all back and say I want another one...