Just wondering - is there any chance he is getting too much caffeine from you? Some babies are really sensitive to it, and a bit passes in to breastmilk - and then you get a situation where a feed wakes them up rather than helping them sleep.
With my DS if I have more than one tea a day I get several wake-ups overnight rather than our usual just one...And it's a nasty cycle because if you are up 4 times a night with your bub then you may well feel like you need coffee to cope with the day!