I have the same kind of feeling of pressure  right in the middle of my sterum. It feels like something is pushing out, or maybe I have to burp but can't. Mostly I have to move around then I will feel it, like if I lean forward it hits me like gas pressure or something. I went to the ER the first time it happen...it's not painful it's just lots of pressure that can be painful depending on how hard it hits me. But when I went the ER they couldn't really find anything wrong. My heart was fine!! which is what I was WORRIED about. They ruled it to be Muscular, but why now? I don't do anything different then usual. I hope they know what they are talking about, because i'm thinking if it was muscular it would have gone away by now you'd think. That was 3 months ago. I am only 29.