When i exercise i feel pain in stomach and heart beat rapidly,i feel breathleness when climb stairs or run or on heavy exertion, i had taken ECG and tread mill test everything is normal, also i am suffering from GERD and hyperacidity . i am 31years old. i had done blood sample tests, BP,sugar all are normal. i am 81 kgs with 172cm height.can i know causes of breathleness