Thank you very much.
First thing is if the diarrhea has been going on for this long then something is causing it and just trying to treat the diarrhea is not going to work since diarrhea is a symptom so all you are doing is covering the problem.
One of the first things I would suggest is deworming the cat. Intestinal parasites can cause continuous diarrhea.I like the SafeGuard brand dewormer for an over the counter dewormer. This can be purchased at most pet stores.
The Natural Balance is a great food but I would switch formulas just in case this is due to a food allergy or intolerance or things like IBD. Natural Balance has a limited addition line that is grain free with a different protein source. I would suggest trying the duck and pea formula. Now changing food can take up to 8-12 weeks to work so do not give up to soon.
In many cases adding additional fiber into the diet will help firm the stool. YOu can do this by using 1 tablespoon of canned pumpkin(not pie filling) to his food daily. Metamucil 1 teaspoon daily can also be added to canned food.
You can use the Children's Immodium only 1/2 teaspoon 3 times per day but you should not use this for more then 2 days.This drug can be toxic if given in too high a dose so no more then 1.5 teaspoons daily.
There are several places pet owners can go for medical care in NY if they do not have the funds.
I will give you this information in case you can not get the diarrhea under control.
Animal Care and Control has low cost care
NY Human Society try here first
Here is information on a new low cost mobile unit
MVA Hope Foundation, Rochester (veterinary care assistance)
ALL 4 PETS: Limited to Western New York (veterinary care assistance)
NY SAVE Inc. (veterinary care assistance)
I hoe this helps, please reply back if you have additional questions or concerns