I Am Suffering From Heart Palpitations/flutters And Have Been Since

I am suffering from heart palpitations/flutters and have been since around February this year.
They seem to have started after I was ill with flu, with me having to visit a doctor due to pains in my chest when coughing/sneezing that went on for months. I was prescribed anti inflammatories as he was sure that this would stop the pains when I coughed/sneezed.
For the most part I have found this to be true, however, nothing seems to have stopped the palpitations. I gave up smoking 3 weeks ago and if anything, they seem to have gotten worse.
They usually start in the afternoon, and continue through the night, they are not always at the point where they are waking me up, but I have has some uncomfortable night where I have been waking up in a sweat (to the point where I have to dry myself off in the middle of the night)
I have had no health issues up until this, but it is getting me quite worried. I am 31 years old, around 5'5 and no more than 12 stone in weight (although I am one of those people who does not weigh themselves regularly)
Thank you