Sharing Our Innermost Thoughts

I had really low grades in my last 3 exams, especially in math. I used to get 2 questions wrong out of 20 questions but now… I can’t even get half of them right. This only happens in exams though, not when I am just studying. When the exam starts, I suddenly get stressed and solve random equations and questions without sorting them out, Even when I am able to solve it, I make some dumb mistakes and after not being able to solve the question even when I could, I skip that question and try to solve another one and whoa, there is not enough time for me to go and solve that question again. So, when the exam ends, I try to solve it again out of curiosity and find out that if I gave more attention and read some things right, it would take seconds for me to solve that problem. Even after solving all of them, some of my answers are still wrong because I didn’t give enough attentin, or simply didn’t notice some things. You may say, this is not important, grades aren’t important, they don’t affect your worth, etc. But in my country, they do. If you are wondering, just check the Turkish LGS 2021 Maths paper and if you happen to solve one of the hard questions and get it right, then congratulations, you are smarter than a 13 year old kid. Anyway, I always wanted to go to a good high school, one that you have to get 450 points out of 500, which I could have said that would be possible if I keep up my good grades, but I couldn’t. Now I don’t know what to do, I haven’t told my family yet, they still expect me to go to the high school I just talked about, but it is impossible with this grades anyway. This way, I am not going to have a good job when I grow up. I can’t even sleep because I think about this all the time. I don’t want to do things that I used to do. I only want to study, which I can’t do properly because my mentally ill elder sister won’t stop shouting at me and beating me up, she won’t leave me alone since my grandmother died last week. I told my family that my grades have been going down, but I haven’t told them it was this bad and I was messing up every single time. I asked them to find a teacher to guide me spesifically, or send me to a private teaching institution, which they think is unnecesarry. I feel really bad, all my teachers are going to be really mad at me, I don’t even want tonorrow to come. What will I do?