I am a 48 year old female. Intermittently, when I do something active like run up the stairs at home and then sit down, I feel an extremely strong pulse in my lower back. It definitely feels like my heartbeat and it is strong enough as to feel painful and I have to grit my teeth until it ends. Usually lasts 10-15 seconds or so. This is new. Is it anything to be concerned about? I am on blood pressure meds.