I'm not sure what the average is, but some people just have narrower skulls than others. It's the cheek bones that determine this. I have wide cheek bones, which makes my face look more round than others. You shouldn't worry about the shape of your skull though... ...the great thing about life is that things aren't the same everywhere you look. If we all had the exact same shape of skull, how boring would that be? Please try to be appreciative of your body. It's obviously difficult sometimes to see the same person in the mirror every single day, but it's possible to freshen yourself up by changing your hair-style or wearing different clothes.
I seriously doubt that there is anything wrong with how you look, ErichFranz. I know only too well, however, how easy it can be to see the 'bad' things when we look in the mirror. A thing I try to remember is that perfection is simply non-existent. If you look around you, there is nobody who is truly perfect looking. We are all different. The problem when we look at ourselves in the mirror is that we magnify the slightest of imperfections.