I Am Experiencing An Abnormal Feeling In The Middle Of

I am experiencing an abnormal feeling in the middle of my chest. It could be described as a feeling of heaviness that lasts for a few seconds and is uncomfortable. It comes and goes. It started yesterday and has continued throughout today. I have had this before but never lasted this long. Is this cause for concern? I have never had heartburn so I can not equate it to that. I do take medicine for high blood pressure and am an otherwise healthy 69 year old female who is very active with bicycling and gym workouts.