I think you should clean up you lines, those drawings look very good but the hairy lines hide the accuracy of your ellipses and perspective. also avoid to make the face a flat surface, i has a curve to it.

These are a good start. I suggest you draw 'through', like a wire frame, so don't just chop off one side, but also the other one, which is usually not visible. This helps to find the vertical middle line of the head, which I believe is your main problem for now. Also, consider drawing a little bigger, keeping your pencil sharp, to go for a cleaner construction.