Hello,
Fleas are the biggest reason for hairloss in cats that we see at our clinic. Even if you don't see evidence of fleas, it only takes one to start the snowball effect.
As Tiger mentioned, using a topical flea control such as Advantage is highly recommended. Unfortunately, this alone will not solve the problem.
Once an allergic reaction to fleas has begun, the best way to get it under control is to get an allergy injection (depo medrol). This will bring immediate relief for your cat and should get the reaction under control quickly.
Feliway is excellent for cats that suffer stress-prone personalities. Also, Rescue Remedy administered by mouth or in water (2 drops once daily) is great for easing anxiety. Rescue Remedy is a homeopathic remedy which is safe for cats and can be found at your local health food store. A bottle is usually about $10 - $15 dollars.
Sometimes dry winter weather can cause itchy skin. Try adding a teaspoon of cod liver oil to your cats diet. Also, feeding a high quality diet such as Iams Hairball will help any skin/hair issues your cat may have.
It certainly doesn't sound like Ringworm, thank goodness!
I hope your cat starts to feel better soon.
Regards,