heart problem

I am 19 years old boy who is overwieght my heart beats above normal speed as i can feel my long heart beats . i want to get rid of my owervieght by excercising but my heart dont want me to do so because wen i excercise my heart beat increases rapidly and i get faint most of the times . i am suffering from high BP problem. i have headaches most of the times as ican hear my head nerves beating me plz give me some advice i have checked my cholestrol it is on border line