My Cat is eating her self alive over grooming , etc!!?

[Ashes]

She has been Way over grooming herself. too the point she now has a sore wound that is now a scab on her spine (near tail) and is going bald there. Vomiting constantly. I Just took her collar off today and found a ton of these bumps all around where her colar was (why i took it off) it was a leather small dog collar. Im watching her right now licking herself ,grooming whatever. its really worrying me idk what i would do without her! Shes only 3 1/2 yrs old. Shes pretty much still a baby. Shes always been a mean cat but i like that about her this has been happening for the past month or so. shes an indoor cat has never been outside. also shes fixed , when i first got her at a year old she was a problem cat was on prozac (got her from a woman that worked at an animal shelter / vet) i weened her off her medication within that month. I Know i should take her too a vet but i do not have the money to pay for it. I really need to help her!!