Heaviness in left side of chest.

Since past 3 months I am noticing slight heaviness in my left side of chest. Whenever I bend down I can feel that heaviness but it goes immediately when I get up . Also now a days I can feel heaviness at same point when I try to cough. 2 months ago I have consulted one of the cardiovascular in Lilavati Hospital and he asked me to go for ECG,stress test,and few more blood test. My all reports were normal and he asked me not to worry and asked me to join the gym and do some physical activity since the I am doing some physical activity at home without any issue but heaviness is still present at same point on my left side of chest ..sometime I get panic attack thinking that I may die because only I know what is going on inside my body ...if i explain you properly whenever I take a deep breath I can feel that heaviness also when I cough I feel the samething ..because of this panic my cough get worse and stress level increases and it is getting worsen day by day but I can do my regular activ