What Causes Feeling Of Heartbeat Below Sternum?

I have been having reflux type problems, having a constant nagging feeling like air or something is trapped from my throat to down under my sternum and below toward my left side under my ribs. Today I can feel a strong heartbeat below my sternum and possibly a lump. I haven t felt comfortable in weeks and seems to be getting worse. I ve tried Prilosec and tums thinking it was acid reflux but it hasn t help and now feeling a heartbeat below my sternum has me more worried. Could this be a hernia?