I had problems getting my milk supply up with my first born you need a good lactation consultant - phone your hospital or Leche League - that is the best and you will find wonderful support and care. It can only improve hang in there it will get better but you need someone who can guide you and who you can phone for advice.
All the best - don't give up
PS my son use to do the same as your little bub - sleep for 5 hrs - and just snack for short period. I had to wake him every 2-3 hrs and basically keep him awake for 40 min to feed even cold cloth wiping him down not to fall asleep - it took a bit of time but worked and my milk supply came right.
I second what erins_mom said. You need to make sure you are getting 500 extra calories a day to keep you supply up. I have never tried it but I know health food stores sell tea that is supposed to increase milk supply. I would contact a doctor before doing that though, just to be safe.
Good Luck and dont give up ;)
drink alot alot alot of water before and after nursing!!!!
start making mothers milk tea you can get it at a health food store drink it with ice even but drink it!! eat alot of fruits, grapes, straws, apples, blueberries!!!
fluids are the key!!!
no caffeine this dehydrates you also not good for baby!
contact la leche league in your area and someone close to you can help you further!!!
best luck!
jennifer