It looks like a pretty nice drawing, but the dodge and burn tools are your ENEMIES!!! Don't use them. Really. They'll keep sucking the blood out of your pictures until there's nothing left...take it from me ^_^' Try darkening the initial tones that you have and using them for your tones of shade. It's all a matter of practice before you realize what works and what doesn't.
Other than that, there's another shading issue, regarding the placement of your shadows...with this pic, you would probably be better off switching the 'shine' in her eyes and place it towards the left side, as most or all of the shadows seem to be coming from the right side, where you have your light source (indicated by the eyes in this picture) It's all a matter of consistency...choose one light source and stick with it throughout the pic, or it'll end up looking...quite funky..again, practice is the key here...it should become second nature to you eventually...Not bad at all though, practice practice practice! (I'm lame that way...)