I Have Been A Regular Smoker For Almost A Year,

I have been a regular smoker for almost a year, and a day ago I was smoking and 5 min after I was done it felt as if my heart was pulsating and so I just feel asleep thinking it would go away, I wake up the next morning and feel the same as I was the day before, and now it feels like my heart is burning and it is speeding up and slowing down, I am not sure what it is and I am afraid to go see a doctor