are you modelling from reference? and what style are you going for, realistic or toony?
If it's realistic then I'd definately recommend reference images

looks like from the cheeks down and the top of the head needs rounding off (look at somebody's head from below to see what I mean for the mouth/jaw area). More definition above the eyes and the top of the nose. The neck should also be far wider, nearly the width of the head.

Good start though and hopefully your having fun with it