You currently seem to be shading reasonably, but per object. And in addition to that, some objects have different lightsources than others. Face lit from front, (our) left arm from the top left, right arm from the lower right, pants and left leg again from the front etcetera. So I marked down some light direction errors here in coloured arrows; and am also curious as to why the elbow-pit appears to be at the red circle halfway the lower arm as opposed to... the elbow.

So first I did a quick attempt fixing some shading, and then I'd like to show you that you should bring the total volume more to the front, by applying a more global shading layer. This latter is done with a nasty photoshop edit, so it should be done more correctly and with more care, but it can be taken further than is shown here. What I basically did while doing so was pay attention to the compositional lines and shapes of the image. From the top of the head we can shade a cylindrical shape going straight down to (our) right arm and hand, and let that split up at the neck into a cylindrical shape that is curved towards (our) the left leg. Looking at the actual shape and potential 'swooshy lines' that make out your image and the way people look at it, can be accentuated with applying shading on a larger basis than the piece-by-piece you seem to be doing now. Look more at the whole!