Ed34 got that right :) Talk to your doctor, they will know what test to do etc., to get to the bottom of what you are feeling :)
Palpitations is such a general word and doesn't really mean anything specific. It really means you feel aware of something irregular with your heart rhythm. So many things can cause palpitations, such as anxiety or even drinking caffeine. What you need to do is establish if there is a serious underlying problem by perhaps organising a holter monitor through your Doctor. You wear this for a given period of time so it can record a trace of your heart rhythm during the palpitations. This will give the Doctor clues as to the reasons for your sensations and the best options for your improvement. You will be surprised at how many things can cause palpitations, even a build up of gas in the stomach.