I hope for everyones sake your cat isn't pregnant.

I do not blame you for having an animal which needs to be altered as you are a minor but why won't your parents help you ?

Surely it would be cheaper to get her altered than to keep having to deal with kittens and further health care cost associated with Mommy cats.

If it's a money issue, maybe you can speak to your local vets and shelters. You might get an offer of cheap or free spaying. As it will save the shelter dealing with future litters from your cat.

I know you have housed past litters yourself and that was the right thing to do but there will be a limited to the number of kittens which can be adopted via your mums work. Eventually everyone who wants one will have one. Any further litters will then end up at local shelters.

Best of luck with your kitty.
Please, Please, Please look into getting a cheap deal on spaying. I'm sure if you explain people will be willing to help.