rant, pls dont abuse me

so I'm writing to the glow community basically because I have nobody to talk to. I'm 19years old and been through quite alot in my short time on earth. my parents split when I was 3 years old and I was made to believe it was my fault and spent the rest of the years of my life having to pick and choose between both of my parents, my mum would tell me awful things about my dad in hopes for me to grow not to like him and my dad did the same about my mum. Finally when I was 16 I moved out. where? to my boyfriends house, for this I was criticized and told I would end up a deadbeat and I would go nowhere. now I am 19 have a job and 2 dogs and my own house I share with the same boyfriend I have been with since 15. my mother has had one job all her life, she is 47 I think.. she works part time as a shelf stacker for a grocery store, as she works night shifts she believes that I should be the child of hers out of the oldest 3, (25,21 and me 19) to babysit her youngest child, (10) my half sister she has a different father who IS a deadbeat. so every 2nd day of the week and all weekend my 10 year old sister is at MY house, dont get me wrong I dont mind helping out but this is becoming a problem. 21 is always having friends over and partying and my mum feels like 10 is a burden on 25, so I have to have her all the time, i have just finished speaking to my mother about the upcoming week and said i can't look after her child and she has blown up and carried on and said "just take her with you it's too bad". I am having serious mental health problems at the moment and my mother has told me "get over it your life isnt as bad as mine" so basically I'm raising her 10 year old as my own BUT I'm not allowed to have mental health issues because my life isnt as bad as hers!!! she is the one who chose not to ever get a job and live off government payments in a government house, not me. she is forever complaining about how my little sister is always being bullied but she refuses to do anything about it. I have offered to pay for everything to change the poor girls school and she wont because it disadvantages her (mum).

anyways I just needed to rant because I feel like jumping off a bridge. thanks.

EDIT; I love my little sister with all my heart and I feel terrible her dad isnt around, she is a wonderful girl hence the reason I'm trying to move her to a better school