My mum is so lazy and never does ANYTHING?

So i'm 15 years old, and I live at home with my mum, and two younger siblings. My mum goes to work, comes home, and plays games on the ps3. She just ignores everything around her, and that's all that she seems to care about. My siblings are brats, and whenever I ask them to help me out with the cleaning if ive got alot of homework to do, they start screaming, and all my mum does is sits there and yells at them.. she doesn't even get up. Even when she's home all day on a day off, she doesn't do anything. I come home and everything is just so messy.. She's always yelling, my siblings are extremely badly behaved and I can't live like this anymore. I clean constantly, while my mum just does nothing.. she says that she's tired and she yells at me when I ask for help. I understand that she is tired but so am I, and i'm practically running a family here, while trying to keep on top of my school work. My friends/ other people have said that im like the mum. I don't go out on the weekends either, because while my mum is working I look after my siblings. No-one appreciates me, and I can't handle my life anymore. I don't know what to do and im really falling behind in school because i've not got the time to effectively study & im getting very depressed, so it's very difficult to keep motivated to get good grades. Honestly this isn't even half of my problems, it's just some of it. What can I do? :'( btw I doubt that my mum will listen to me if I try and reason with her, she will just yell and swear at me, or agree to change things and never do it Thanks