For some insight regarding enlarged aorta. Normally the size is less than 4.0 cm, and if and when it enlarges to 4.0 and greater it is considered an anuersym. With an aenursym, the condition is monitored closely, and if the size reaches 5.0 cm, there may be an need for intervention to prevent a rupture as the vessel wall is thin. Also, if the size grows 0.05 or greater in a year there may be intervention.
Shortness of breath may be related to a low cardiac output due to aorta valve non-compliance. With an enlarged aorta, and individual should not be lifting anything heavy..the reason is the blood pressure can spike and cause a problem with the vessel.
It is difficult to provide more information without knowing your general health conditon, taking medication, concomitant health issues, medical history, etc. Anytime there is shortness of breath, that can be serious depending on the circumstances that cause the condition, etc.
Hope this provides a perspective, and helps you with any further consultation with your doctor if necssary. Thanks for the question, take care.
Ken