@outlander,
family dynamics are difficult and complex. We often have habitual ways of relating to family members that become fixed and ingrained. We do not even realize how and when these patterned become set... but they are very difficult to change.
You may try to change your way of relating to you Mum or another family member and find that they are completely at a loss to deal with that change. They may rally against you. Their behavior towards you may become even worse that what is was to begin with.... for example, they may try and get you to take on even more responsibility and 'guilt-trip' you, if you don't.
Sorry, @outlander, I am just talking in general terms... and giving examples. I don't really know what goes on in your family and I am not an expert on family dynamics. I am just thinking of what has happened to me in the past.
At one point, I got way too involved with my parents and their arguments and trying to be the peace-keeper. I was basically taking on the responsibility of pacifying both parents, all the time. This was not healthy for me!
I had to take a step back, and if that meant that my parents' arguments got even worse for a while, then so be it. It was their problem, not mine.
Think about ways you can take a step back from your family, @outlander- even if it's only small steps to begin with. Eventually, you may like to move out of home. I wonder how old your sisters are, and can they start taking on some responsibilities? Even a twelve year old can cook a simple meal and do a load of laundry.
I think you said that your Mum works full time, but I'm sure she can care for your sisters on her days off/weekends, while you get out of the house and do something just for you.
It's not easy to make changes, but don't give up, @outlander.
Please do talk to a professional about this. You may need a lot of support to make some changes.