First of all, welcome to the forum. I hope you stay because there are many good people here.
I am truly sad for loss of your father. Likewise, I lost mine a few years ago and it was a struggle. Even now I miss, him but we are told that the passing of time allows the healing of sad memories. Only your mother is probably feeling the same acute sadness that bereavement brings, and on top of that she has to keep your father's business going and that means working long hours on top of having to trudge round busy supermarkets and come home stressed to cook dinner. While she switches off after a long day's work, she de-stresses playing Candy Crush; I know the symptoms all too well.
When Dad was diagnosed with cancer, he shut off on me. Mother had moved to another country, for their marriage had ground to a halt and I was at a horrible school not helping. As Dad entered a world of his own, so I decided to tackle him. Instead of being confrontational which would have seriously annoyed him, instead - I sat down and wrote him a special letter. It was in pen and ink in my best handwriting. I drafted it out and left it it a few days for my anger and sadness to dissipate. Then I returned to writing again and left the letter on his pillow on his bed.
You could do the same to your Mum. Write her the most heartfelt letter. Choose your words with tenderness and understanding if it be possible. Draft it out first like I did Dad's, removing all the anger and frustration, the words that would have got his back up. Writing your Mum a letter likewise and leaving it somewhere private so she can be alone to read it.
When Dad read my letter he came and wrapped his arms roound me. We cried, we really cried big tears. But that letter opened the floodgates to the beginning of mutual understanding. It brought Dad to realise how much he had been neglecting me. My letter helped bring about a nicer daughter-father relationship; I am very glad I wrote to him.
I hope that if you write your dear Mum a letter, then she will take notice of you and begin repairing that which must be so painful and difficult right now.
Your school might have a Peer Support programme. This is where older students who have more life experience get to talk to their younger peers to listen and to provide practical help. You Head of Class may know of something similar. You could ask them.
My heart goes out to you.
Anna Mouse
PS. While I remember, there is an excellent forum for young people and older which you may find helpful even if you live in another country other than the UK.
The Student Room
When I was doing my online degree course, they were very helpful.