You are suffering from palpitation, an unpleasant awareness of the heart beat.
The most likely causes of your palpitation are:
Anxiety: Anxiety is the primary cause of such awareness of heart beats. These anxiety attacks are often accompanied by feelings of breathlessness, warmth in the body, impending doom, etc.
Caffeine: excessive caffeine intake can add to this.
Smoking: Nicotine is a known cause of palpitation.
Alcohol: excessive alcohol intake can cause this.
Anemia: low blood hemoglobin levels can lead to palpitation.
Thyroid: high thyroid hormone levels can lead to palpitation.
In your case, it is most likely due to anxiety and nothing else.
You should make a number of lifestyle changes which will help you.
Decrease caffeine (coffee, tea, cold drinks) and alcohol
Try to relax about this, the more attention you pay to this, the more likely that you will feel anxiety about the heart beats.
However, if you cannot control the anxiety about the palpitations on your own, it is best to see your doctor.
Discuss about having your thyroid and hemoglobin levels checked though that is probably not required.
Most important is to treat stress/anxiety and insomnia.
You should discuss with your doctor about taking Beta blockers and other anti anxiety medicines which will help you overcome this.