[M22]Need advice raising and caring for my two little sisters aged 8&10

I've created a throwaway for obvious reasons but here goes.I've been tasked with raising my two little sisters because of a tragedy that put me in this situation a couple of years ago.For the past 2 years i've been raising my two little sisters by doing everything a housefather and mother would do, buying groceries, doing dishes, cleaning the house, making food, buying clothing, bringing the kids to school and park to entertain them, trying to teach them good behaviour, etc...My problem is that there are periods in my life where it just becomes too much and i can't handle the stress duo to many reasons personal reasons and additionally the kids stressing me out by defying me, not listening to my commands, lying to me, not studying when i tell them to etc etc...Lately i've just fell into a downward spiral and i can't keep going, i feel like i'm becoming a negative influence in their lives and that i will fail to make good human beings out of them. I don't do what i preach is the best way to describe it i guess.I have agressive bursts whenever the kids do something that aggrevates me and i lash out on them by screaming at them and being agressive, i almost never resolve something by being kind with them but by being strict with them. I do tell them why they did something wrong and why i was angry but i feel like they will hate me for it when i'm older.This is the complete opposite way that i am with regular people, people know me by my gentle behaviour and non-agresiveness, but it just seems i become the opposite when at home.The 8 year old let's call her Christina, is very gentle and generally does everything i ask of her, she also has been learning how to do the dishes and regular housework to help me out and relieve stress for me, she's also more of the social type unlike my other 10 year old sister(lets call her Ella)Ella is whom i'm most concerned of, she's introvert, does bad at school unlike Christina and is very rebellish which doesn't help because that just puts me in a situation that stresses me out more.So to summarize what i need help with.-How do i teach kids how to study well? -How do i teach kids not to act rebellious and respectfull towards their elders? -How do i relieve the stress i'm going through? -How do i explain to them the situation we're in? -How do i prevent them from becoming like me and how do i handle the stress and outbursts?Maybe it's just that i need a place to talk about it it, i don't know. But i feel like it can't get worse just by asking some advice here.Thank you via /r/Parenting http://ift.tt/2btlSkU