I feel very competent in my proportions, anatomy, and ability to construct but no matter how hard I try my sketches always feel like a scratchy, sloppy mess

I'm entirely self taught thus far and always felt like I never developed good, fundamental peniciling techniques that is holding me back.

Pic related. Just a sketch I was working on the other day. Thought I was on the right track--and maybe I'm being my own worst critic--but the more I come along the more I feel like its just becoming a rough, smudgy mess and I'm taking a totally wrong approach.

Could anyone recommend a tutorial, video, book, or anything that is all about how to control the pencil and the best approach to drawing at a fundamental level?