The recent anatomy work is very nice. In progressing with your forms you have to break from the symbolism that we all develop initially. So, for that, I'd recommend you drop anatomy for now, and apply your time fully to studies from life (in pen - for confidence).
i'll be very direct, just so as to make it more obvious for u...to encourage u to take tat step to improve coz all of us knows our shortcomings on a certain lvl but just find it hard to push ourselves. ur lines r too thick and wifout weight thus making ur sketches blocky n flat. i myself draw wif a sharpened pencil all the time, preference plus it forces me to draw my construction lines light and create forms wif weighing the lines.maybe u can try tat but no guarantee it will work, i'm a newbie too. just wanna help. hope i was tactful enuff.
Listing - I have done some life studies (may not be apparent in above sketches). I'll do some more and see what I can come up with. Pen eh? I'll see what I can do :d
emptyvessel - I know exactly what you mean. My lines are thick b/c I usually go over them 3-5 times and then move on. But yes, I too use a sharpened pencil with every sketch. I use 2 different sharpeners just for the job. I think I'll have more confidence in my lines and see where that takes me
I agree with the other crits. draw more life. Do your studies one day then the next day go to the mall or cafe or something and just draw people who walk by or people sitting having coffee. Get a feel for the movement.