I saw your post on bfing so hopefully some of the moms there can help you with your supply, if it is low. I also used to worry my lo wasn't getting enough milk because I didn't feel 'full' during the evening, but the moms wrote & said that at night is when you have the most of the hindmilk which is rich & thick. We will naturally be more full during the morning, but it has a lot of foremilk which is like water. At night, even if you don't feel 'full', they still get the good stuff (hindmilk) full of calories & fat which should help them sleep longer lengths.
Is he nursing for a long time when he wakes up at night? Let us know how he nurses during nightwakings.
Kathy