From the American Academy of Pediatrics;

The following are some possible warning signs of feeding problems, and should be discussed with your pediatrician.

Too Much Feeding:

• If bottle-fed, the baby is consuming more than 4 to 6 ounces (120 to 180 mL) per feeding.
• She vomits most or all the food after a complete feeding.
• Her stools are loose and very watery, eight or more times a day. (Keep in mind that breastfed babies normally tend to have much more frequent and looser stools.)

Too Little Feeding:

• If breastfed, the baby stops feeding after ten minutes or less.
• She wets fewer than four diapers per day; particularly if she has begun sleeping through the night, she may be feeding inadequately (since most babies feed at least once during the night), and may urinate less often and become mildly dehydrated.
• She has infrequent or very hard stools in the first month.
• She appears hungry, searching for something to suck shortly after feedings.
• She becomes more yellow, instead of less, during the first week.

Feeding Allergy or Digestive Disturbance:

• Your baby vomits most or all food after a complete feeding.
• She produces loose and very watery stools eight or more times a day or has blood in the stools.
• She has a severe skin rash.