I agree with the second post - that if your hair already doesn't need much moisture, then only co-washing will give it more moisture and weigh down the curls. I have photos of my hair before CG and it is full of volume. Now, though, it isn't as much. I'm still quite new to CG though, so who knows what will happen once I get into a routine I like.
Maybe try shampooing ocassionally and see if it makes a difference. As long as your hair is healthy it doesn't matter if you can't call yourself CG