Is my goldfish dying?

I got my one-eyed goldfish Sammy on October 24th 2008. Recently I moved him into a 10 gallon tank by himself. This past week all he has done is lay at the bottom of the tank and not swim. I've been trying to do everything to help him out. Test the water PH, ect; everything I've read in the message boards. Is there something else I need to be doing to help him out? Is he just bored or dying? I'm worrying about him and just want to do everything in my power to make him happy.