I am so sorry to hear that your mum is seriously ill with breast cancer.
You must definitely talk to someone about it all. Things only get worse if we bottle difficult emotions up inside us and even if no-one can make your mum well again, it is easier to deal with if you share your emotions with someone you trust. This could be your mum, someone else in the family, a close friend, maybe a parent of a close friend, a teacher or someone else who may be close to you.
Don't think that you shouldn't talk to your mum or others in the family about the situation. This is very common and we often find that everyone in a family wants to protect each other and they think that it's better if they don't talk about things that are difficult. This can of course be helpful some times as we can't be sad or talk about difficult things all the time. But it can also make it harder for everyone as everybody is thinking about the same thing but no-one talks about it. We often think that if others don't talk about it then they are doing okay and that if we start talking about it then we will make them feel upset when they didn't need to be.
Particularly parents often underestimate the difficulties that their children are going through in situations like yours - often because children and young people can be very good at hiding their emotions and pretending that they are okay. Do try and talk to your family when you are feeling low as it is usually better for everyone to have an open communication about it than carrying all the worries alone.
You could also try and 'talk' to someone in the forum on the riprap website as many will be in a similar situation. You may feel that your friends don't understand what you're going through and the riprap forum can be of great help in talking to someone who knows what it's like.
Also, please do get back to us again if you think we can be of any further help. Certainly, if you don't have anybody around you to talk to, we can point you in the right direction of getting in touch with appropriate people.