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I see you have not gotten a response yet. I can help you, and I am a veterinarian, but I can only answer questions here. I can't make calls for the website. You can continue to wait for an expert who can make calls, or I can help you here.
Is your cat neutered? Has he had his vaccinations?
When a young cat like this is not eating, and losing weight, it is usually not parasites. Parasites will cause weight loss, but doesn't usually cause a cat to stop eating. In a cat less than a year, I would be worried about the three serious viral diseases we see in young cats: feline leukemia, FIP and feline AIDs.
If you look at his gums, are they pale in color or a normal bright pink? I would take him to your veterinarian for a check up and if your vet thinks it is the right thing to do, test him for these viral diseases, especially if you think his gums are pale in appearance.
As I said above, I am not able to make calls for the website. It would be very unusual for hairball to cause weight loss and not eating. Vomiting can be seen with infections, and internal blockages (which are sometimes seen in severe cases of parasitism) as well as hairball.
You can get hairball remedies online, or in pet stores or at your veterinarians, but hairballs rarely make a cat sick and not eat. Good that his gums are pink.
The offer for a phone call was automatic from the website, not from me. I am in the US and can't call you even if I could make calls for the website!
How is Norty doing? Was my answer helpful? I hope he is better; let me know.