Reflux Esophagitis (Gastroesophageal Reflux Disease - GERD): This condition is common in infants and can cause feeding difficulties due to the backflow of stomach acid into the esophagus, leading to discomfort, pain, and the symptoms described.

Tongue-Tie (Ankyloglossia): A condition where the tongue is anchored to the floor of the mouth, restricting its movement and potentially causing feeding difficulties, including a weak suck and fussiness during feeding.
Laryngomalacia: A condition characterized by soft and floppy tissues of the larynx (voice box) that can partially block the airway, especially when inhaling, leading to symptoms like choking or gagging sounds during feeding.
Oral Motor Dysfunction: Issues with the coordination and strength of the muscles used for sucking, swallowing, and breathing, which can lead to feeding difficulties and the symptoms described.

Pyloric Stenosis: A condition where the pylorus (the passage between the stomach and small intestine) thickens, blocking food from entering the intestine, which can lead to severe vomiting and dehydration if not promptly diagnosed and treated.
Esophageal Atresia or Tracheoesophageal Fistula: Congenital anomalies of the esophagus that can cause severe feeding difficulties, including coughing, choking, and inability to pass food into the stomach.
Food Protein-Induced Allergic Proctocolitis (FPIAP) or Other Allergic Conditions: Allergic reactions to proteins in breast milk or formula can cause blood in stool, fussiness, and other gastrointestinal symptoms.

Congenital Heart Disease: Certain heart defects can lead to feeding difficulties due to increased energy expenditure and decreased cardiac output, leading to symptoms like fussiness, sweating, and poor weight gain during feeding.
Metabolic Disorders: Rare conditions like galactosemia, where the body is unable to properly break down galactose (a sugar found in milk), can cause severe symptoms after feeding, including vomiting, diarrhea, and failure to thrive.
Neurological Conditions (e.g., Moebius Syndrome, Congenital Myasthenia): These are rare conditions that affect the nerves and muscles, potentially causing feeding difficulties due to weakness or paralysis of the muscles involved in sucking and swallowing.