You sketch too light man, try to work it a little more. And also when shading use as long strokes as you can.
I find it useful to only shade in two directions, one is diagonal bottem right to top left, as im right handed, the other is parallel to the edge of whatever i'm shading.
Looks very nice tho, has good form, but definatley work the shading a lot better, and it will make you look way more pro ;)