My cat is a 1 yr old female...

Question
My cat is a 1 yr old female and is not spaded.  I haven't had her checked
out by a vet yet.  Just today I noticed on both sides of her spine is sore
and she meows when it is touched in the slightest way.  It starts about
the middle of the rib cage back to her hips on both sides.  Her
climbing/jumping skills are non-existant at this point.  She hasn't been
eating well for the past week.  Before, I filled her bowl every day, but
now it's every 3-4 days.  She would roll & play before but now she sits on
all four like a sphynx.  I think it's because that is the most painless
position for her.  She drinks alot of water and her litter pan consist of
mostly urine.  When she was eating well, the litter pan usually had 2
piles and a little urine.  She doesn't chirrup & greet me in the happy
kitty way anymore.  No unusual hair is missing but I have noticed that she
isn't grooming nearly as much as before and she is dirty.  She hides in
any place she can find and doesn't play as before.  Also, would another
kitten help her socially, maybe bring her spirits up?  What is the most
common fatal feline disease?  Leukemia?
I hope this is enough information.
please help my ill-kitty  

Answer
Without an examination by a vet, it is hard for me to be very specific.  Having said that, it sounds to me like your cat is in heat.  There could be some kind of spinal injury if there is unrelenting pain.

Feline leukemia is one leading cause of fatal disease in the cat, but there are many others including FIP and FIV.