Hello. welcome to HCM. Chest pain, breathlessness and fast heart rate while walking or during any exertion can be due to angina. When you walk or exert, the heart s oxygen demand increases and hence the blood flow to the heart also increases. If the arteries are having blockages, then this supply is hampered leading to chest pain, breathlessness. The heart tries to compensate by beating faster hence the fast heart rate. Breathlessness in your case can also be continued by asthma. I recommend you do an ECG and a 2 d echo for cardiac evaluation. If both ECG and 2d echo are normal then you must undergo a stress test. It tests the functional capacity of the heart and can predict presence of blockages in the heart. Also I hope you are compliant on your asthma medications and inhalers. I suggest you do a PFT (pulmonary function test) also to evaluate the functional capacity of the lungs. All these together will give a definite reason for your symptoms. Wishing you good health Regards.