Ok, its stressful, but stay calm. If babies crop isnt working correctly, feed some Applesauce with Apple cider vinegar in it,, 6or 7 cc"s of applesauce with 5 or 6 drops of BRAGGS apple cider vinegar in it. The applesauce should be warmed to 102 F to 104F..massage the crop to get it moving, but not too hard to cause anything in there to come back up...youll need to do this 2 or 3 times a day until the crop clears,,, but still feed regular formula after an hour to two..after the applesauce..you can also give a few cc"s of just plain warm water and massage the crop,,takes longer, but will help..baby have a sour smell coming from its mouth? Also, keep baby warm, body temp does affect crop movement. He may have aspirated, not all hope is lost! If the vet gave you antibiotics, it's a fail safe in case anything is wrong. What were you given and how much, how long? I wish I was there to help you. I'm wishing you the best! Keep us updated.