Hi Helen,
Sorry to hear about your problem.This bug affects me from time to time as well, and i have spent many hours experimenting to find a fix for it.
Here is what always works for me.
1.Login to a quiet sim such as Itress or Jublad.
2.Open the advanced menu by pressing crtl+alt+D.
3.Select advanced>character>character test>test female(or male).
4.After a few minutes you can wear your skin, shape, clothes, ect,as you normally would.
5.After a few more minutes you will see a "blurring " of your avatar ,followed by a "sharpening" of the image. This is the sign that the textures loaded properly.
Another trick i use to avoid potential embarrasment is to use an alt account logged in at the same time and place to use as a "mirror"of sorts to be sure the textures have "baked" properly.
Hope this helps and feel free to contact me inworld if you have any diffuculty with my instructions.