Hey balls01,
I think there are a couple of issues in the face and head. First, I believe that you have the old chopped off skull syndrome on this piece (
http://bos.typepad.com/carpenter.jpg). It is harder to notice in this one, because if you measure from the tip of the head to the chin, the eyes are in just the right place. However, her head is tilted forward, so the top of the head is actually not at the physical peak. Plus, the hair takes up a bit of room above the top of the head. Next, you are not paying attention to shading in the face! Unlike the body, where you thought about light source and stuff, on the face you are reverting to drawing symbolically.
On your nose, there is a dark line going around the left edge of the nose. This is not how the light would effect it. The light source is up and to the left, so the light would highlight the left side of the nose, and it would cast a shadow on the upper lip. The lips would not be equally dark as they are in your piece, the top lip would be in shadow, the bottom in light, and then the bottom lip would create some amount of shadow below it. You have ignored the whites of the eyes, and just made brown blobs with a highlight. Also, the hair would cast some amount of shadow on the forehead (I maybe exaggerated it a bit, but I think it works).
In my initial edit I tried to address I problem I think you have with your pelvis, but I explained poorly. I gave her a thick butt, but you can solve the problem and retain the skinny look you desire, you just need to move the leg down or thicken it so that there is room for the pelvic bone. Look at this picture:
See how much room there is from the belly button to the back of the thigh? Yours needs to be increased, whether through a thicker leg, or moving it down and extending the abdomen.