Toxic Environment?

I'm a 29 year old woman recently diagnosed with ASD (Aspergers) and I feel the need to vent here on something that has just happened today.

In my post diagnostic session, I was told about ways I can manage my social battery and that sometimes I need to be selfish and avoid doing certain things if I think they will affect my 'charge' level that day.

  I live at home and for the past few weeks or so my mum has been sick and spent most of the day on the couch in the living room. I have also been sick but am recovering, but still feeling a bit washed out. Every morning I have been getting up and doing chores like washing the pots, vacuuming and cleaning the kitchen. However because I am still tired, it takes me all morning and I need to have a nice leisurely breakfast before I can face the day. This hasn't been a problem as I can usually get it all done before my mom even leaves the living room. This morning, however she got up before I did and while I had my breakfast she suddenly started berating me about not helping round the house and when I tried to explain she started screaming at me and saying how she's fed up of being a slave and that I should stop being lazy and use my initiative more to help out round the house. I ended up frozen to the spot in confusion and trying so hard not to scream back at her. In the end I fled upstairs while my dad tried to calm her down, and proceded to self harm. 

Now this isn't a normal occurrence as my mom has mental health issues of her own which mean she is a Jekyll and Hyde at times. She has a B12 deficiency which went untreated for so long it has affected her mentally. She takes injections but the slightest stress can either plunge her into depression or she becomes aggressive and verbally abusive.

So my problem is, how can I be 'selfish' and decide not to do certain things that day if sometimes I am criticised by my family for taking the time to recharge myself? 9 times out of 10 they are understanding, just like 9 times out if 10 my mom is a sweet, loving caring person. It's the days she becomes a verbal monster I can't cope with..but I can't escape. I'm trapped in the house because my social and anxiety issues mean I barely leave the house and I'm reliant on my parents for a lot of things. What can I do? I feel obligated to contribute to the household by helping out, but sometimes I forget to do certain things or I don't dont do them quick enough and then I'm criticised for being more devoted to my own 'special interests' than in helping out round the house. And heaven help me if I use my Autism as an 'excuse' for not cleaning the bathroom today...which I really can't face doing after the stress of this episode, but I don't want to be yelled at again...

I suppose there isn't really anything that can be done, but I just needed to vent a bit for the sake of seeing this in writing and wondering if anyone has advice...aside from "Leave that toxic environment"