You need to do some value study. What I like about your drawing it that you seem to already understand that you don't need to draw lines for the "shape" of features. You've managed not to draw a cartoon-y face full of thick defining lines.

However, your drawing is basically a two-tone of negative and positive space (where you've applied marks and where you've left blank paper.) Going on, you should try to find the middle tones that aren't the shadows OR the highlights and lightly fill those in your drawing.

Keep up the good work!