Hi im 18 years old. My exams are going on currently and suddenly these days i've started having sleepless nights due to my heart beating very fast. Sometimes i think its a heart attack or cancer(i used to drink and smoke). But then later wen i went to the doctor he told me everything was fine with me which surprised me. Some say that im worried by my exams but honestly im well prepared for it and there's no such fear.
Please suggest how to end this feeling. Is it due to smoking/drinking? Is my health at risk?