Chris,
Henry III does not drain me completely, so I try to pump after he eats. Keep a bouncy seat, blanket or Moses basket, etc. by your chair where you can place baby while you pump after a feeding. If you find there is nothing left after feeding and pumping, I would say you don't need to pump after feeding. However, if there is still even just a little bit, you might want to try to pump after feeding as much as possible. I know it is hard. Keep up the good work!
Aloha,
Christina