HI there, I'm sorry that you are sad at the moment, I'm also sorry that mum and dad are screaming at you a lot, maybe they have a lot of things going on in their lives that are stressing them and they are having trouble coping with this themselves?
I don't think mum will just run away and leave you, I think your mum and dad love you very much they just have a lot on their plate at the moment. Do you have a councillor at school you can talk to? Or maybe a good teacher you can trust and have a chat with?
I guess from your post that you are the oldest child, so mum and dad probably expect more from you than the younger children.....that can be hard sometimes and it's easy to get a bit resentful of that.....please don't run away it's a dangerous world we live in ok....
I don't know if I have helped in any way or not, just remember you are not alone, post on here and there are lots of people who will give you good advice...I'm sending you a big hug ok "HUGS" cos you sound like you need one......best wishes to you honey .....shannon