Welcome to the forum and to a really nice place to have a chat and get some support on what I can hear is a really tough time for you at the moment, I am so sorry that a person so young has to be responsible soley for the cleaning and order of the house.
I would like to say though that you are most certainly not gross, you are a person who is going through a really overwhelming time. Can I say to you though, the voices in your head are just that, voices, noise and they are not welcome, they are not the truth and are not to be believed. It takes some practice and some strength to shut this noise down and you can even say out loud "i hear you, you don't matter, you are not real and you can leave now".." I am worthy, I am beautiful and I matter"..I am wondering if you have some things in the day that you can reach out to that give you some joy and happiness? Something you can turn to to make you feel good when these things happen? I love to paint and to write and also music and reading, they make me feel really good.
I am not sure if you feel comfortable to speak to your mother in calmer times and say to her that you do try your best to do what you can around the house, that you could use some help and feel it is alot for one person. Could you tell her that it hurts you when she yells at you and makes you feel very bad about yourself? I understand she is your mother but you seem to be doing nothing to me that warrants being spoken to in a way that makes you feel so very bad.
I am sorry that school was your only escape and now you dont have that as part of your day, it does make things hard to manage when your time of peace has been taken away from you. I hope you can still get your school work done and that online schooling is not too stressful for you.
I hope to chat to you some more rumii, we are here to listen and to care, you can chat about how you are feeling and will not be judged or hurt here.
Hugs to you