baby sleeping during nursing...

Hello.  My son is constantly falling asleep while nursing, despite my best efforts to keep waking him (skin to skin, rubbing back, collarbone, tickling feet, neck, etc... etc...)  Needless to say, I worry that he is not actively eating enough, especially since I attempt to nurse on both sides and when I put him down he is sleeping much less than he has in past weeks.  For example, when I put him down, he typically sleeps for 3+ hours and I have to wake him to nurse, but over the past few days he continues the new pattern of waking after only an hour or even less (of course making it hard to really get any rest).  At our 2 week appointment, he had still not come back up to his birth weight, so we had started pumping and adding an extra bottle following feedings to help him start climbing back.  (At a follow up, he gained 6 oz over a 5 day period doing this).  This is another reason I've very concerned about him falling asleep, since his weight has already been a concern.  

Perhaps he is going through a growth spurt or something but I'd love any advice others have found to remedy sleepy newborns.  I'm starting to think I should continue pumping more as opposed to EBF.