Hi,
How are you? Are there other symptoms aside from dyspnea or gasping? Aside from asthma or reflux, other possible causes include COPD, heart problems, panic disorder or pericarditis. If it persists, have this evaluated further. Additional tests such as ECG, chest x-ray and some blood tests may help determine the underlying cause. Were you able to follow-up with your doctor regarding your past history of breast cancer?
Take care and do keep us posted.
I guess no one cares. Oh well