Hehe, yes, this one turned out a little mortifying, but the lighting is quite good! Well, looks like the teeth are growing out of the lips, rather then being part of the skull inside. The head itself is more like a ball with a cone for a neck and the ears suggest a different direction than the face. But, again, something about the shading style is really neat! Again it's sort of wooden, which adds to the creepy, haunted doll feel.
You could practice form and volume with line drawings, possible, maybe explore a skull and then ponder how muscle, fat and skin would go over top of it. Always keep perspective in mind. Maybe draw three skulls next to each other, each facing in a different direction. It would be a challenging exercise, but it might strengthen your observational powers and clarity.
Maybe I'll drop a little example for you here?
...but I don't have any doubt that you'll master this, too, sooner than you think!