Panic Attack: The patient's anxiety and shortness of breath, despite having good oxygen levels and clear lungs, strongly suggest a panic attack. Panic attacks are characterized by intense fear or discomfort that reaches a peak within minutes and includes symptoms such as palpitations, sweating, trembling, feeling of choking, and shortness of breath.

Anxiety Disorder: Given the patient's anxiety, an underlying anxiety disorder could be contributing to the shortness of breath. Anxiety disorders can manifest with physical symptoms, including respiratory distress, even in the absence of a panic attack.
Hyperventilation Syndrome: This condition involves rapid and deep breathing, often associated with anxiety, which can lead to symptoms like shortness of breath, dizziness, and tingling in the hands and feet. The patient's good oxygen levels and clear lungs support this possibility.
Asthma or COPD Exacerbation: Although the lungs are clear and oxygen is good, it's possible that the patient is experiencing an early or mild exacerbation of asthma or COPD, which could cause shortness of breath without immediately affecting oxygen saturation or lung sounds.

Pulmonary Embolism (PE): Although less likely given the clear lungs and good oxygenation, PE is a potentially life-threatening condition that must be considered in any patient with shortness of breath. It can sometimes present with minimal initial symptoms.
Cardiac Ischemia or Myocardial Infarction: Shortness of breath can be a symptom of cardiac ischemia or myocardial infarction, especially in patients with risk factors. The absence of chest pain does not rule out these conditions.
Pneumothorax: A spontaneous pneumothorax could cause shortness of breath and might not immediately affect oxygen saturation or lung sounds if small.

Vocal Cord Dysfunction: This condition can mimic asthma and cause shortness of breath due to abnormal vocal cord movement. It's less common but should be considered if other diagnoses are ruled out.
Neuromuscular Disorders: Certain neuromuscular disorders, such as myasthenia gravis, can cause respiratory symptoms, including shortness of breath, due to muscle weakness. These are less common but important to consider in the differential diagnosis.