Don't feel bad hon, remember that yorkies are extra sensitive to temperature, so they will shiver at the slightest breeze, and cook in the slightest warmth! That's how it seems with my one anyway!
So you did the right thing cutting hair for summer and letting it grow for fall/winter. I'm doing that with Willie. His hair was chopped for summer and now it's growing back for fall/winter. It's already starting to get cooler here!