Hello ED,
I'm sorry that you're in this situation so young. Most kids your age are in college, still struggling though.
You don't have to worry about money if you use it wisely. I used to be awful with it 'til my ex husband one day decided he wasn't paying for shopping any more, or bills or for anything else. I had to do it and I had to buy presents for the grandkids and kids for birthdays and Yule Tide etc. Living on $350 a fortnight made it hard. He spent all of his money on gambling and alcohol.
I learned to budget and lay away for birthdays and Yule and I bought other gifts to pop away when I had the spare money. I reduced my outgoings to the bare minimum amount and was able to save. I still do not spend $5 notes, I save them in a tin with $1 & $2 coins and I'm always happy when I count it up. I used to do it regularly but now I just do it every now and again and I get a lovely surprise; it makes certain that I have a very nice cushion to land of if an unexpected bill comes in, or if I want to buy a treat or if I have to go somewhere in a hurry it gives me money in my pocket.
If you like you can try these tips; stop buying things for other people, buy only what you need, save 10% of your income and place it into a savings account, don't spend $5 notes and see where you are in say 6 months....Good luck with it...
I don't think your grandparents don't care, and I don't think you really think that either do you? They looked after you the very best they could and I think they still do what they can