you should work a bit with proportions then, try looking at male (or female) bodies and try to reproduce the proportions in the paper. Not really drawing the image you're seeing, but comparing each body part sizes separately and then try make the complete figure later, with the correct sizes and distance between each part
I know it sound hard and not even I can do it properly but focus in understanding proportions, I just gave some examples of how I would try to practice (and how I actually do)
not the best of examples but might be of some help´
also I can tell that what you're doing with the head is reproduce a common technique to draw heads without fully understanding it, I'll try to make a step-to-step tutorial of how I usually visualize in 3D my head schema/sketch later