Gastroesophageal Reflux Disease (GERD): This condition can cause shortness of breath due to acid reflux irritating the lungs, nausea from stomach acid, and difficulty eating due to esophageal discomfort or pain.

Pulmonary Embolism: Although more commonly associated with sudden onset of shortness of breath, it can also cause nausea and, if severe, lead to decreased appetite or difficulty eating due to respiratory distress.
Chronic Obstructive Pulmonary Disease (COPD): COPD can lead to shortness of breath, and in advanced stages, may cause nausea and difficulty eating due to increased work of breathing and potential for respiratory failure.
Heart Failure: This condition can cause shortness of breath, nausea (especially if there's associated liver congestion), and difficulty eating due to decreased appetite from congestion or medication side effects.

Myocardial Infarction (MI): Although classically presenting with chest pain, an MI can also present with shortness of breath, nausea, and difficulty eating, especially in diabetic or elderly patients who may have atypical presentations.
Pneumonia: Severe pneumonia can cause shortness of breath, nausea, and difficulty eating due to high fever, respiratory distress, and potential for sepsis.
Pulmonary Edema: Acute pulmonary edema can present with sudden shortness of breath, nausea, and difficulty eating due to fluid overload in the lungs, often requiring immediate medical attention.

Eosinophilic Esophagitis: A rare condition causing difficulty swallowing, nausea, and potentially shortness of breath if there's associated asthma or allergic reaction.
Mitral Valve Disease: Certain conditions like mitral stenosis can lead to shortness of breath, and if severe, may cause nausea and difficulty eating due to decreased cardiac output and potential for pulmonary congestion.
Scleroderma: A chronic autoimmune disease that can affect the esophagus, leading to difficulty eating and swallowing, and potentially cause shortness of breath if there's associated pulmonary fibrosis.