Hey well I think the problem lies in the basic construction, try to slow down on the shape fo the spheres, and remember you have to take the sides away like cutting the sphere in both sides. This will affect the basic shape and flatten the sides of the head. One thing that helped me a lot is to get a bunch of portraits from pinterest ( try to get the ones where the whole head is shown from diffferent angles) and then trace them on photoshop and try to spot the areas of changes of planes and how each feature interact with each other in perspective. I hope this helps Keep rocking that stylus 
