Re: one breast empty!
Welcome and congratulations on the new baby!
As long as you are feeding on demand, seeing adequate wet and poopy diaper output (here's a handy reference: http://www.kellymom.com/bf/supply/enough-milk.html), and seeing adequate weight gain, what you describe should probably not concern you.
Most women start out overproducing milk. It's nature's way of making absolutely certain the baby or babies get fed. But after a while, your body detects that milk is being left in the breast after the baby is done nursing, and it starts cutting down on the excess production. Making extra milk is a waste of energy and puts you at increased risk for plugged ducts and mastitis, so the adjustment of supply to meet demand is actually a desirable event.
When supply adjusts to meet demand, many women notice that they stop feeling "full," stop leaking or at least leak less, and that their letdown sensation diminishes or disappears. This can happen in both breasts simultaneously, or can affect only one breast. Despite the new empty feeling, there is milk in the breast, and assuming your baby is nursing well, he is capable of getting it if you just allow him unrestricted access. You probably do not need to pump. And since pumping is NOT a good gauge of supply (Every mom responds differently to the pump, pumps vary in efficacy, pumping is a learned skill, pump output varies widely based on when you pump, etc.), pumping instead of nursing will not really tell you much about how much your baby is getting at the breast.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"