Fitting clothes is weird. I have garments in M, L, and XL, made by the same manufacturer, all of which fit me fine. I have a size M dress that is, if anything, loose on me and a size L dress that is too small -- from the same maker! None of these clothes are tightly-fitted, but still, it makes no sense!

The business with the turtlenecks sounds like what a friend of mine calls "going shopping in your closet." It's nice fun to find things that you'd forgotten about that you can still wear.