Re: SOS--Severe gas/abdominal pain, spit
Definitely possible for a baby to be sensitive to soy and not cow's milk! Generally it's the other way round- sensitivity to cow's milk seems to be more common than sensitivity to soy- but that doesn't mean that's the case for your individual baby. So I would definitely consider cutting soy from your diet or at lest reducing the amount you're eating.
FWIW, true lactose intolerance in a baby is incredibly rare. When a baby has a problem with dairy, it's with the proteins in animal milk, not with the sugars (and lactose is a sugar). Human milk is full of lactose, and babies are designed to consume lots of it. Babies therefore produce plenty of lactase, the enzyme that breaks down lactose and makes it digestible. Lactase production declines as you get older, which is why lactose intolerance is common in adults but almost unheard of in babies and children.
That being said, sometimes babies go through spates of temporary lactose intolerance, when the amount of lactase they produce is not sufficient to handle the lactose in their diet. This can happen when mom has an overabundant milk supply (which would fit well with a forceful letdown issue- forceful letdowns almost always come from oversupply), or from illness caused by some sort of infectious agent. If you don't have a milk oversupply, some sort of illness could explain all the symptoms you're seeing.
Definitely don't stop nursing, mama! This is almost assuredly fixable, and while I am sure the gas is horrible and you hate seeing your baby hurting, it is not too high a price to pay for the benefits you will both get if you continue to nurse.
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