It’s like a baby asking “I’m struggling with not getting my nappy changed often enough and have developed a bad rash that doctors are concerned might start to become seriously infected”.
OP if you read this, you are not alone in this feeling. As a 25 year old growing up with a single Mum, I had my own battles.
You are far-far-far away from any permanent damage from having excess fat.
If you shop with your parents, start nagging for more veggies and fruits.
Instead of sitting around after school. Do some stretches in your room, or whatever. If you can safely, go for walks more in the afternoon.
You’re still a kid and as much as that sounds dumb, you wanting to become healthy now is some ground breaking shit.