I don't know how to treat my sick cat
Did you call the vet?
I can't ask a vet, they know nothing about my cat
After four years of veterinarian school, they likely know more than you or I.
I will just let my cat die rather than call the vet.
I don't understand your reasoning. You adopted the cat. You're obligated to feed and care for it -- you need to take your cat the the vet.