I am such an idiot.

Whap. Whap. Whap. Sound of ruler whacking my head

Several weeks ago, I had a complete refit on my bike!
I had it refitted to a more aero, aggressive position. I didn't even think of it, other than, "Gee, I just added 2mph on my flat cruising speed... cool."
It never entered my head that the extra speed came from somewhere even if I didn't feel any extra exertion at the time. Indy's post just reminded my of my positioning. Whap whap. (KSH, I didn't word it correctly - my average is about 15-16, but my cruising speed is 17-18mph).
Gee, I knew my body was slow-twitch, but I didn't realize my brain was, too. Thanks for all your advice, gals. And I will watch my pace and caloric intake! Whap.