It seems to me that the symptoms for these are pretty much all the same, so how can I tell? My 3 month old spits up excessively (but not so much when she takes about 3 ounces at a feeding from a bottle). Her poop is still yellow but has gotten more watery in the last few weeks. She cries most of the time when she spits up. She doesn't cry everytime we nurse but it does happen more in the afternoons than in the morning.
Oh, and she is a little over 11 pounds, takes Zantac once in the morning and once at night.