What Could Be Causing My Severe Fatigue, Low Stamina, Gynecomastia, And Exhaustion Even With Minimal Activity?

Doctor, I have barely done any serious physical activity for 8 years I am 26 now with Gynecomastia. I cant walk even 100 mts without panting.Low stamina and a feminish body make me feel uncomfortable.My life is going from failure to more.......I feel physically and mentally exhausted each moment in my life........and feels very sleepy......Whenever I smoke a cigarette, I feel like I cant move a bit and my whole body burning and craving for some life..........Please help me.....May God bless you.....