mum argument ( answer back quick please !) i know it's long but still please answer it :) :(

my mum lately been work a lot while my dad doesn't and she was going through a stress full time. My 4 year old brother has been getting on my nerves and for a 12 year old i have a small temper ( he always has to be first at everything getting dressed , eating , washing his teeth ect.. plus i share a room with him !) yesterday my mum was angry at me cause i shouted at my brother saying " i don't care if i got dressed first in to my pj i am tired !" and i he went and told on me ( he does it all the time ) my mum told my brother to hit me . and i said " fine them u can do what ever you want to me ! they she busted out shouting " you stop choppsing me off i am your mother not friend " ( but the thing is my friends are nice to me understand me and listen ! she doesn't ) then i got depressed because she expects more everyday she says i only have to take the rubbish out but i do way more . i look after my bro and he cries all the time and if i want to go out i can't coz i have to take my bro i am like a second mother even if my mum is home !! i understand sometimes yeah but not all the time ! my dad blames everything on me he doesn't do any thing him self and bring it all out to me ! so i ended up crying in the bathroom ! ( my mum isn't always like this she can be really funny and nice and sweet but not all or even most of the time and my bro can be nice to spend time with too but if you say something wrong or do he will just cry .
when i came back from school i was walking today on my own with my earphones in listening to music i came back no one even say hi or hey or any thing so i went to my room and i was hungry i went to the kitchen and i was sining ( my sining is not too good but i still love doing it ) and she said stop singing and i didn't she came in and said it again but i just said free country , she sent me outside ! :0 so i did walked out quite far from my hose but i could still see it i was waiting for my bro to pick him of the bus ( too early but i didn't care ) then she called me in so i went and she said " don't you understand i am in a very hard time do you want me to go to hospital with a heart attack ( i was thing no and after i while said no ) then she said what have i done to you ? i didn't say but the truth is she hurt my feeling and at some point it feels like i hate her but i don't it's just sometimes she annoys and makes me cry ! please help and tell me what could make this better coz i love my mum and i don't what her to be sad !!