Hello and hope you are doing well.
Inadequate oxygenation can produce symptoms of breathlessness, as the body tries in an effort to compensate for the decreased oxygen supply. The breathlessness could be due to cardiac or lung disorders. Breathlessness on exertion could be due to the decreased lung function. Again in cardiac disorders the heart is unable to pump the blood adequately, more so when subjected to stress like exercise. Certain systemic disorders like anemia, diabetes, vitamin deficiencies and thyroid disorders can aggravate these symptoms. So please consult your primary care physician who may ask for an EKG or a treadmill test to rule out a cardiac cause for the dyspnea. He may even ask for blood tests and an X ray chest. Lung function tests could further help in evaluation.
Hope this helped and do keep us posted.