Take a deep breath,try to relax and talk to your self. understand why it is important to do good in ur exam. Ask urself what will you lose if u failed in ur xm,is it worth or not...
Try meditation,think positive
Think how will u feel if u passed with a wonderful grade 😀
There are so many people who look up to you, and so many times there may be things you did have helped or saved someone from their darkest place without knowing, things seems tough but you are worth it because you know you wouldn't let others down like how you are right now, so just go step by step, make a time table try the pomodoro technique
So take a deep breath and relax think you want to study just for 15 min then do something which you like . Ex I will study for 15 min and then I would watch tv . This always helped me so hope it helps you . But never give up and believe in yourself.