Should I pump one side or both sides of my breasts during midnight if my baby only nurse one side of my breast?

You could try pumping the breast that is unused while baby is nursing on the other. Lots of my friends do that, because it saves time and apparently they can get alot of milk pumping with baby nursing on the other side. When baby breastfeeds, relaxing hormones are released and this helps with the release of the milk during pumping. It takes some practice to balance both baby and pump but once you get the hang of it, works like a dream :)