Should I put my mother in an assisted living home?

I have 3 other siblings. Two are too selfish to help my ailing 82 year old mom. My mom and my developentally disabled 60 year old sister live together. No one drives. I suffer from Major depression, see a psychiatrist and therapist and take about 8 medications myself. I am the only one that takes my mother and sister to the grocery store, doctor's office, haircuts etc. I do not have a lot of money. My mother and sister combined have more money than my husband put together. I have to push myself to get out of bed, drive over 20 miles to get to my moms house, drive them around and then drive back home. I know my mother feels she is broke and my mom has taken care of my sister all her life. Even my mother's doctor said she will need to go into a nursing home soon. I am at my breaking point and can no longer do this. I help them in every way I can and it is not good enough. Somehow I feel that my mother expects this from as my husband and I do have a nicer home then they do. I haven't worked for four years and just get by. I feel we're supporting my mom and sister and our own home. It is too much pressure for me. My mother's doctor told me that my mother's health is declining and she is showing signs of dementia. Any suggestions?