Am i burning oil?

I took my car in for an oil change - i was a little overdue, and it turned out that i was a quart low on oil. I know i am not leaking any oil because i dont see a puddle under my car in the morning. Is this normal?

Also, my valve cover has a tendency to be somewhat moist around the oil (yes its screwed on right) cap and spark plug cover - could there be oil coming through the valve cover or something??