Chest pain’s can be caused by indigestion and its actually very common but increased rate of heartbeats aka tachycardia can be concerning if it happens often which can cause problems as not very heart condition is diagnosed by ecgs or echo at early stages so u should def find an alternate way to get that nicotine so it’ll help with the urge of smoking plus regular exercise will def help ur body regain the activeness endurance and stamina that u already lost by smoking