Ohh I hadn't even thought of expressing and giving it to him in the bottle ! That's a great idea. He is due to wake soon so I might try that with him instead of forumla. I've only seen him mikl drunk after formula (and it is ohh so cute), but it might just be that it takes longer on the breast than on the bottle and I might not be letting him go for long enough.
Also, when your boobs are really full, expressing off the watery foremilk will mean that when he latches on he gets more of the fatty, filling hindmilk. The more hindmilk, the fuller he'll be and the more 'milk drunk' and sleepy. If your boobs are heaps full he may just be gulping skinny foremilk then getting full of gas and fussing. Hence why he seems 'hungry' again quickly.
A lactation consultant can help explain the foremilk/hindmilk balance and how to work those boobies

AND expressing first means you get the milk flowing for him, so when he latches on its already ready to go, which really helps when you have an unsettled hungry baby. Express and then when you have a drop on your nipple, go to latch him on, giving him a 'taste'.