Help for fine wavy weird hair

My hair is naturally wavy, but I have long, fine hair. Now here is the weird part....if I don't put loads of product in and diffuse it, my hair will not dry naturally wavy. It will have some kink to it, but not much. I never have to straighten my hair. If I just brush it out when wet and blow dry it it will go straight no problem.  However, if I get caught out in the rain, my hair will go super wavy...it makes no sense! Maybe it's the chemicals??

Anyway, I use Paul Mitchell mousse, an apple sized amount on my hair and then diffuse it with my head upside down. Here is what irritates me, certain sections of hair will wave so beautifully, almost corkscrews, and then other areas like the back of my hair will be kind of a kinky frizz.

What is the solution here? Is there something I am not doing? Or is it that some people just don't have nice looking natural waves?   lol