Is your hair 3B or 3C?
One thing I'd suggest is to read Lorraine Massey's book "Curly Girl," where she talked about the actual structure of curly hair. I learned that the differences between 3A versus 3B/C are greatly affected by length, and everyone's hair responds differently to various lengths. I am wondering if your hair is the type that curls more when it's shorter, but straightens when it's longer. In contrast, my hair is a 3A where it is curlier with length, and straighter short. At one time when I had a chin length bob, it was so straight anyone who hadn't known me before the cut wouldn't have believed I had naturally curly hair.
I am also thinking your hair would fare better with a halfway down the back length, or even waist length, rather than to the behind length.