My life is hard and I'm finding it hard. please help...?

I can't deal with this anymore. I'm 15. My little sister is 7 years old, she has lung disease, brital ashma, kidney problems. She has a wheel chair and in my house we have a stair lift. She can walk but she gets out of breath and stops breathing. (She has been resusitated 4 times) She has been ill ever since she was born and basically lives in hospital. She has had soo many operations and tests done but they still can't sure her. I hate hospitals and she always crys for me to be their when she is canualted (put on a drip) she has had to be put in special care (in a coma) for a few weeks because she couldn't breath for herself, she's always soo poorly. My household is always at the hospital so I wake up for school home alone, go to school, come home and no one is home and then I go to bed when I'm home alone. It gets too much to handle. My brother was in a really bad car crash a year ago and the hospital thought he was dead. He was in a hospital about 3 hours away from home for about 7 months. He was really poorly. My dad has a problem where he has prequent strokes. And now I'm in the scare of maybe being pregnant, I think I just want someone to love and take care of (I know it sounds silly but I can't do that with my family as I don't get no attention off of them) with my boyfriend, he's really supportive over the pregnancy thing as we both work. I dunno what to do anymore