I simply don't understand why this happens in my game.

My characters always seem to be scaled down.

I'm playing this female vampire which is only barely taller than women from average sized races, while being significantly shorter than her fellow Nord females.

http://i.imgur.com/YIzyJpXh.jpg

This also seems to be present with my other characters. They are always at least a bit shorter than npcs of the same race and gender.

I'm on the PS3.

You already have a thread on this which you posted in last week. Spamming can get you warnings.
http://www.gamesas.com/topic/1503760-bugged-size-scaling/