Underweight Breastfed Baby - Any Tips on How to Get Him to Gain?

It sounds like you're doing pretty good. He should be sleeping more, but I don't know if that would effect his weight, the book Healthy Sleep Habits; Happy Child can help with the sleep.
I know the bottle gives a sense of security because you can see him drinking it, but babies are way better at getting the milk out than pumps so try giving it to him straight for a bit. If you want to know how many ozs, you can rent a scale like they use at the drs office and weigh him before and after feedings. The fattiest part of your milk is the hind milk, it comes in the second half of the feeding, so try nursing on one side only per feeding, let him stay on that side as long as he wants and the breast seems way empty. Also make sure you are getting enough fat in your diet, if your not getting any, then neither is he. 2% or whole milk, full-fat yogurt, cheese, make sure you're getting enough. No offense to drs, but a lactation consultant or LLL will be more help than your ped. Go ahead and try all that, but remember that percentages are just statistics and averages, and he is a baby. If he seems happy and is smiling and holding his head up on schedule and his length and overall weight keeps increasing, some kids are just skinny. Don't worry about it too much.

I exclusively pumped for my twins for one year. You will have to keep the same schedule (every 3 hours) and pump for a significant amount of time (I pumped for 20 min each time).

If you supplement, you will still need to make sure to pump so as not to lessen your volume.

Good luck!!

T. - I can't stress enough how important it is to exclusively breastfeed your baby if you want to be able to continue breastfeeding. Your breasts need the stimulation only your baby can provide in order to maintain a great milk supply, a pump just will not do it. Many moms, myself included, make the mistake of thinking their babies are not getting enough milk and begin supplements and pumping. Pumping should only be used in between regular feedings to boost milk supply or when you have to be away from your baby for a feeding or two. If you wish to continue breastfeeding, supplementing with formula can be a slippery slope to early weaning. Trust that your body will provide more than adequate nutrition for your little one as long as you breastfeed as often as your baby seems to need. Some days this will be 10 times and some days maybe only 4 or 5. Every baby and every woman's breasts are slightly different. Also, make sure you are taking good care of yourself, eating frequently and drinking plenty of water (sleep helps too, when you can get it!). If you have a hard time getting enough calories in a day -try drinking an Ensure every day to supplement. Also, breastfed babies tend to be long and lean and this is not a bad thing. There are studies showing that breastfeeding your child can actually reduce the risk of childhood and adult obesity. I am a firm believer in breastfeeding and its many benefits for your and your baby. You may want to visit the La Leche League website for more support, http://www.llli.org. Also, if you continue to have concerns regarding breastfeeding or your baby's weight discuss these with your pediatrician and/or a lactation consultant. After breastfeeding my two daughters, I know how hard breastfeeding can be, but I also know how beneficial and rewarding it can be.

Best of luck to you and your little one.

If you are continuing to pump, maybe try nursing him after you've pumped....the hind milk at the end of a nursing is the most fat-laden and calorie rich. That would also help increase your milk supply if you are worried about that.