Perhaps you know it already, but I'll give it a shot. Do you often flip/mirror your image while drawing/painting symmetrical things? This imideatly reveals anything wonky.
I like this work! Especially #3 in the third post, seems elegant, stylish and what my friend calls "vectorish" (as if made in Illustrator).
May I reccomend an exercise? Have you tried drawing from casts or sculptures of a human head? A mannequin's head is also good, or you can find some simple 3d app and draw from a 3d model.