I am a 43 year old female, ex-smoker on HRT. For the past few months I ve been getting a really strange feeling right in the middle of my chest - the best way of describing it is like the feeling you get when someone, or something, makes you jump . It s as though I ve been frightened of something or I ve been hit in the middle of the chest - but from the inside. It can happen at any time of the day, but most frequently at night when I m trying to sleep. Can you please help because I m getting really scared that I m about to die?