extreme fur loss and loss of appetite

Hello all. My cat is 18 years old and always been an indoor cat, she was fit a healthy(if not a little overweight) a month ago so much so that everyone thought she was only a young cat. In the last month she has dropped all her weight, loosing fur at an insane rate in large clumps. She has bald patches on her back,neck and belly and her paws have thinned so u can see the bones and where the claws retract is clearly visible. She shakes her foot a lot yet I can't see anything other than the fur loss. She has black dry gunk in her ears that looks crusty as if its dry skin and fur in there. She has also lost her eyelashes and the beautiful cream eyeliner she had is now black for whatever reason. Her blood test results showed a slightly low wbc but all other functions were fine. The vet has said it is old age. Which I don't believe as u don't suddenly become old in a month. Could also be stress as my partner moved in around the same time BUT my cat has been all across the country on roadtrips and living in extreme heat as well as different people coming in and out if the house so I don't see why having him move in would stress her as she sleeps with him! Please any advice would be wonderful as I have had her since I was 9 and I am now 27 and we have never spent a day apart.

Have I misread or am I correct in thinking your fur baby has been to the vet and been given the all clear? Sounds to me as if it could be an allergic reaction to something. As you say, it's more likely to be stress as an allergy wouldn't cause the weight loss. Have you changed her food at all? I wound definitely get her to the vet as soon as possible if you haven't already. The problem with older cats and cats in general is that they hide being ill so well.
Hope you get some answers soon!

I'd try another vet tbh. Did your cat only have bloods as a test? Which bloods did they do - all or some? Perhaps an x-ray may be useful too.
I agree with you, it sounds too sudden to be down to old age. I would suspect hyperthyroidism, causes weight loss & hair loss, or too much cortisone which can cause darkening of the skin too. But these are just two of the many posibilities, so please get a second opinion.

Best of luck to you both, hope you find out what's going on soon.