It's exceedingly unlikely you'll have any proper help from us, as none of us are Vets (that I know of), and none of us can diagnose a cat across the internet by just it's symptoms.
I'll be honest and say that it's hard to tell.
It could be anything, from a small infection, to organ failure, a mental condition, or (in the worst case) a cancer/tumour.
I can't suggest much, other than to ensure it has plenty of food and drink available to it, and to perhaps try changing it's current food to some other brand or type.
Does it normally have dry food or wet food, or both?
Otherwise, try to keep it comfortable, but don't panic over it.
Just be aware, that if it wanders off somewhere obscure, it could be a sign it's getting ready to die. Cats quite often try to find comfortable calm places where they can die in peace.
Other than that however, your only option is to get veterinary help. Sadly, Vet care is ridiculously expensive everywhere. If you can push to the costs of the scans, then go for them.
The upsetting thing is, you could pay out a large sum only to find it's a disease nothing can be done about, and it will just cost you more money to have the cat put to sleep.
If it seems like it's in a very poor state of living, the kindest thing to do may be to put it down.
I hope it doesn't come to that though, and I really hope your cat gets better. Sorry to hear you've got this problem.
My cat, of 14 years age, died the other year rather slowly from what appeared to be an eye infection, and turned out to be a cancer. It was rather traumatic. It's a shame to think your cat is also sick.
