"can't you see your mum is having a really hard time because of you?"
Your parents sound selfish, narcissistic to me.
My parents were the same. I had a serious depressive episode when I was 17. As I couldn't stop crying I was unable to go to work. All I remember mother saying was ' Oh no, I aint got you grizzling round me all day have I'
No concern at all.
Made me feel like s##t. You feel like I did, unwanted, a burden.
Well, I can tell you, you are precious, worthy and life is worth it.
Do you take any anti depressants? They may help lift your mood. You need to do well at school get good job and move out asap.