L.C.
Hi D.,
Do you know for sure that he is not getting enough? Is he falling off of his growth curve? Does he have about 6 pee diapers each day? The first thing is to find out if this is really the issue. When kiddos go through a growth spurt, they can be insatiable, and just because you can't get much from pumping, doesn't mean that it's the same when your baby nurses.
There are many ways to increase milk supply. The first thing is to make sure you are getting enough to eat and drink. You need extra calories and water to make milk. Don't worry about losing weight right now.
Second, find ways to minimize your stress level, because feeling tense can decrease your supply. (With 3, I know how hard this part can be!)
If you suspect that your baby's latch is the problem (clucking sounds, popping on and off the nipple, choking, etc.) then see a lactation counselor (IBCLC's are usually the best trained). Here's a list in CO: http://www.breastfeeding.com/directory/states/colorado.html
Another very important thing to know is that 12-4 am is the most hormonally sensitive time for stimulating milk production. So if you're trying to get your baby to sleep through the night, it may affect your supply.
Feeding on demand keeps your supply up, too, because it's the stimulation your body needs to know how much milk to make. Scheduling feeds can interfere. One thing you can do is spend 24 hours back in bed with your baby. On a day when someone else can watch your older child and take care of everything else, you can just relax, snuggle, and nurse, and get back into the rhythm of the nursing relationship.
Also, if you are already introducing any solid food (and you don't need to yet, btw), then make sure your baby gets the food AFTER a nursing session. At 5 months, this probably is less important, since they are likely to just taste things and spit them out, but as they get older if they eat food first and then nurse, they won't be as hungry, and will nurse less, and supply will decrease.
This applies to giving formula, too. Anything the baby eats that is not your milk will mean less stimulation and less supply.
There are herbs that help with milk supply, too, if everything else is in place. Traditional Medicinals has a tea called Mother's Milk that has fennel and fenugreek, two herbs used to build milk supply. You can drink one to four (or more) cups per day (and it is actually pretty tasty).
It sounds like you are really committed to continuing to nurse and I'm sure you can! Make sure you have the support you need, from your partner, from friends, and from a lactation counselor if you need it. And if your baby is losing weight or seeming dehydrated or listless, check in with your doctor to make sure there isn't something else going on.
Best wishes!
L. Caron
(mom of 3 and naturopathic doctor)