What if it isn't so much the story your writing but how your writing it that you can't process correctly from you brain to writer's hands?
Like I already know I stop writing before I start because I can't sit down to write, if I do I leave out a bunch of important details from my head while if I write the details I forget where I'm at beyond the scene I am writing. So usually I record my voice and talk myself threw the story. Then I will write down key detail that will happen later on in the story that I want to put in or think more about. So when I sit down with my notes and my tape from it I end up just writing stuff that sounds like something a fifth grader could write, but coming up with some very interesting dialogues, scenes, characters, and scenarios that would seem to be the perfect base for the next bestseller if only someone with real talent was writing it. Then I start doubting myself as a writer only to "throw down the pencil" and come back to it months later. That's pretty much the cycle to my attempt at a writing career.