Grandmother refusing to go to nursing home. I'm 18 and alone. Advice?

I'm am 18 years old and have been taking care of my 80 year old grandmother for about 2 months now. Her husband has been deceased for 14 years now. My grandmothers daughter (aka my mother), passed away in 2008 and her son (my "uncle") doesn't want to have anything to do with my grandmother or my family and is just waiting for her to die. My father and grandmother have never gotten along, so it isn't a choice for my dad to help me take charge. I am alone on my own with this situation I about about to speak about so any help is appreciated. Two years ago, my grandmother had a very bad leg infection that cause her to fall and had to be rushed to the ER. My father, my younger sister, and I have been left to take care of her dog on top of our own cat and dog, which wasn't a big ordeal for a few months. She was then transferred to a nursing home/rehab center for care while she got surgeries on her leg. She was then diagnosed with a cancerous brain tumor and had to go through tons of chemo. She beat the Cancer and the leg infection, and was then told she needed surgery for cataracts is her eyes (that hasn't happened yet). I did not know about any of these things, because my uncle did not keep my updated because he himself could careless about her and wasn't there to support her. After many calls and pleas for me to help her get out and back home, the nursing home finally was able to get her discharged and healthy enough after a year and a half. I drove her home, went grocery shopping, cleaned her house, cared for her until the home care nurses and aids were able to start visiting her a few times a week. She got weaker and weaker, was barely able to go to the bathroom alone, refused to eat food that she asked me to get for her, and couldn't make it to the phone in time when the aids called to let them know they were coming, so they didn't show up. Multiple times I let the home care know the door was unlocked and they were able to get in. She would always end up on the ground because she was too weak to walk, and I would always have to throw out my muscles trying to help her up (I don't want to admit it but I'm a frail, 110lb female and she weighs 175lb, and cannot lift her like that on my own). One fall last month I needed to call an ambulance, and they admitted her to the hospital. She was discharged and sent home and was fine, but things started to progressively get worse. She wasn't taking her medicine on her own, she wasn't washing herself, and refused help from the aids when the call but insisted I came over to do everything for her. I did when she needed it, but its honestly starting to wear me out a lot. Just this week, she fell again and called an ambulance, but apparently refused to go to the hospital when they came. I haven't heard from her all week, she usually calls me every day, so I decided to stop at her house. I found her on the floor, again, crying for me to help her up. I refused, propped her head up, and called an ambulance, and she was takes to the hospital. The house was a complete wreck, nothing like I had seen from her before, feces were covering the bathroom, and trails of it were on the floor from her crawling. She hasn't been taking her important medication, or antipsychotics. She is a threat to herself but refuses to go to a nursing home. She is not in the right state of mind, and says and does irrational things half of the time. I am afraid for her and her health. I don't want her to live the way she is living. It is also starting to kill me. I lost my job, I can't go back to college, I'm getting physically sick, I'm getting panic attacks, and I am developing extreme insomnia. I have issues of my own such as severe clinical depression and have been trying to battle it for 5 years and finally got to work with a psyciatrist last October. This situation is hindering my ability to get better mentally and is making me hurt mentally and physically. She is in the hospital right now and I believe this is the best chance for me to talk to someone there about this whole mess of a situation. I wish I would have never taken her out of the home. I cannot provide adequate care for her, and I feel bad about that. I want her to be well cared for 24hrs like she needs. I am basically her primary caregiver other than help from her aids/nurse/physical therapist that she sees a few times a week. I am alone, and have no advice from any one else. Any input would be highly appreciated. I'm just worried I wont be able to get her into a nursing home because she continuously screams about the "misery" at the last one and how she will never go back. That is the best option for her, she cannot care for herself even with the help of us, and she needs 24hr care. I need all of the help I can get.