M.A.
Try useing a "Haberman Feeder". You can get this from a Madella breast feeding catalog or through a lactation consultant.It is a bottle that has a dial that controls milk flow and special nipples so that no matter how softly the baby sucks he will get milk without so much exertion. As their strength increases you can adjust the dial and change the nipple if needed to control the flow for a stronger suck. Use until child can suck from a regular bottle and nipple or breastfeed. I used this on my daughter who had low tone, heart problems, exhausted very easily and had to drink a certain amount before she could go home. Found out about this from another mother and have recommended it to several parents that used it with success.