Dear Camille, Sounds to me like the supply is faltering,, which is a
logical result, not enough tissue to support full supply or interruption in
access of tissue to nipple.  Early on enough milk from BF initiation and
hormonal stim and baby small.  As baby and needs grow, supply isn't going
to keep up.  Frequently seen after reduction surgery.  Try archives for
discussion of this. This is why moms -post any type br surgery- need to be
closely followed during BF, esp. reduction surgery.
Baby sleeps because he is hungry, depressed, giving up.  Feed the Baby!
Supplementing via SNS accessses what milk is avail from mom and preserves
the breastfeeding experience.  I've had one mom BF this way and another who
said forget it and switched to bottle.
You want to focus on mother/baby relationship.  This one seems full of
frustration on both mother and baby's parts.  So just feed him.  Mom will
be happy to see gain and baby will be happy to be adequately nourished and
will perk up, respond to mom and begin to interact and develop as expected.
 Sincerely, Pat Young in SNJ, USA