It looks like you have the basic construction step down, so I'd suggest a couple things: Practice, practice, practice basic perspective. Once you can convincingly wrap an rubber band line around a ball and construct spheres, this becomes easier. It's also worth knowing how multiple forms intersect, or "interlock" as Steve Huston calls it, for dealing with the underlying perspective of facial anatomy. Keep at it like an athlete training sport and you'll be surprised at how much better your Loomis heads eventually look. Second, I'd recommend leaving off eyes, mouth and hair and save that for a portrait class. Can't say enough, however, just how much it helps to have mastery over the basic perspective involved in the head first.

It is not sad looking. You can always draw a smiley onto it! Draw some more pears or other fruits. Try and think about the parts you like and which parts you do not like and why. It helps to improve