Well, your lines in your drawings go from leftunder to right upper corner. When I started drawing a lot of years ago I did the same thing. Whit a lot of practice I started to change this technique and now I use curved lines in all my drawings. Than you can create more volume and your portrets will improve a lot. In the making of "Moustache" you can see what I mean. You have to look closely to notice. Hope you don't mind my advice.