If I'm to contribute to this, I have, believe it or not, not only school advise but also mental health advise.
To begin with, school. As XiaoJia pointed out, we teachers are usually helpful if you ask about anything. You have to be brave though. Most are afraid of us for idk what reason (might just have to with us ruining your lives with homework).
As a teacher, I really don't feel good suggesting this, but for someone in your situation it might be good to reduce the ammount of school work by neglecting some subjects for a set ammount of time. Choose wisely which subjects to neglect. I recomend to do it with those in which you feel that you're ahead, or with those that take much time and effort compared to what their grade is worth.
Doing this will let you focus on fewer subjects and allow you to catch up in those. You will feel that you've done a better job, and it will recuce stress if you feel less behind.