I can't take it anymore!!!!

I don't know where to start, so I will start 21 years ago my father passed, I moved 500 miles away from home. My childhood well lets just say not good. 5 years after I moved my mother & grandmother moved to "MY" state. I made a good life for myself an oldest son, put my childhood behind me, I also got married a year after they moved here. 6/7 years ago my grandmother passed, my mom lost her job, had to get a pace maker, numerous other health issues. We were paying for prescriptions, Dr. visits, etc. then she quit paying her cobra, so then we had to start paying more. Told us she couldn't afford her cobra and her other bills on unemployment.My husband gave her a job so she would have income and health insurance. In 2007 we built a house made sure we had enough room for her, she has her own bedroom, living room, and bathroom. We told her to either put the $$$ into savings from her paycheck, or put her SSI check in savings, instead of paying us anything, you guessed it she didn't do it. Taking care of my mother has been drilled into my head that it is my obligation, I am the only child, mined you my parents did the minimal, food in my stomach, a roof over my head, clothes on my back, if I made A's in school they could of been higher A's, I was never going to make anything of myself, etc, my father was an alcoholic and my mom handle that by never being home, yes she was working - she made sure of it. I had things happen to me that NO child should have to deal with, most girls dream of growing up, getting married, kids, I dreamed of getting far away and making my life very different.
Since she has moved in with us I feel I have lost my family, if we ever tried to do anything without her, the guilt trip is massive. People that have tried to become friends with my mom, if she allowed it they disappeared quickly, or they weren't good enough for her. 2 years ago she fell ill had to quit her job, and I left mine to care for her. over the past couple years she has gained some strength and can do alot more then she does, I do her cleaning, laundry, prepare all meals,the only thing I haven't started yet is bathing her, I do more for her then I do for my youngest that is 16 or even my husband. We have gone thru our savings, I can't do enough or make her happy, never a thank you or acknowledgement of everything I have done after all it is my responsibility.
I have lost all my friends they have moved on, my family relationships are struggling. When I talk about going back to work I hear " I can't" - "what am I going to do?"
I guess what started this is 4 days ago my husband was involved in a serious accident, trust me when I say I am lucky he is still here. But what if? I seriously would be in a bad place, emotionally, financially, all the way around, let alone me- my kids! I am at my wits end, my childhood that I struggled to put behind me is now haunting me, my husband or kids know nothing of my childhood, except some of my mom's version, I don't talk about it. I don't want my kids to think badly of their grandma, she has on the most part been great with them.
I want and need my life back, the one I struggled so hard to have.
I tell myself my mom did and is doing the best she knows how. She is doing exactly what her mother did to her to me. I was able to put my grandmother in her place, years before she even moved near me, and had very little to do with her. Of course she had the last laugh, her burial expenses fell on me.
I know my story is confusing, I know I sound like I am having a pity party for myself, I also know I have allowed this behavior, but what do you do when its your mother- even if she wasn't much of one.