For two days now, I keep getting the feeling of large air bubbles trapped in my chest, making it hard to take a deep breath. If I pound/tap on my chest, I'm able to 'burp' myself and relieve the pressure, but it keeps coming back continuously. It has been happening both before and after I eat. I also have a pain in the upper/center of my back. Is this a temporary acid issue, or something more serious related to heart/lungs? 52 yr old female, avg/ low blood pressure, non smoker, otherwise excellent health