can also be due to food allergies(grains) environmental allergies (sprays etc.) flea bite dermatitis, and possibly even hyperthyroidism when its so extensive...best to get kitty a good Vet exam and some bloodwork done, poor little guy sounds like he is really suffering..
Hi Felicia, sometimes cats will do this from stress.
Has there been any changes in the home? A move? New pet? New person moved in?
These will be stressful to cats and cause them to develop nervous habits. Cats really don't like change, but sometimes we just can't help exposing them to it. Now, if there's been no change in the home, have you noticed any other changes in his behavior-eating less, less active, etc.?