I finally got to my drawing class and here's what I got after 4 hrs. I was sorta rushing the shading, because I wasn't sure I'd take another lesson next week. 
it was coal pencil on A2 paper.
The teacher said I shouldn't apply so much tone at this stage. The figure looks too black where it's opposed to the light - infact, the model's right side will catch reflected light and look lighter. Also, at this stage, I should draw more of his face. And, finally, the front plane of the belly should be narrow, I got it too wide. Personally, I'm not happy with the posture - it's somewhat lifeless, not energetic. But: I hope to improve things next Thursday :)
