Dear Christina,
Doctors tend to look for certain conditions in certain groups of people. In a young woman it is unlikely that heart disease is present but nothing is impossible. There are many other causes of chest pain that would be more likely to be causing your symptoms.
Amongst the cardiac causes of chest pain not due to ischemia are: pericarditis (inflammation of the sack around the heart), myocarditis (inflammation of the heart), cardiomyopathy (heart failure) and rarer causes such as coronary artery dissection, acute rupture of the heart and valves and infections of the pericardium.
Gastrointestinal causes of chest pain include reflux (acid from the stomach washing back into the esophagus), gallstones, esophageal spasm, esophageal rupture, varicose veins of the esophagus, strictures of the esophagus, tumors of the esophagus and other less common GI problems.
Pulmonary (lung) causes include pneumonia, pulmonary embolus, pneumothorax, pleuritis and bleb rupture.
Other potential causes are aortic dissection, back and spine problems and musculoskeletal (muscle strain, rib fracture, etc.).
Psychological causes of chest pain are common and include panic attacks, anxiety, stress and mental duress.
As you can see there are a number of potential causes that your doctor will have to work through with you. However, more than likely the cause will not be something serious in someone your age.