Heart beating very hard

So I've had this for a while ... my heart feels like it's beating very hard, not particularly fast or slow but hard! Very difficult to describe but basically I can feel it in my chest and in my stomach and if I lie on my left side I can hear it in my ear! Not all the time, mainly when I lie down! Anyone had this? My midwife seemed unconcerned but just wondering if anyone else has had this or had it checked out by a doctor?