Hey RM26, Check these guys out: https://www.resilientperformancept.com/ They do Postural Restoration, which is likely what you need. Can't promise it'll get rid of the belching, but it'll definitely...
I've got a little insight into what MAY BE going on here, but I need some feedback from anyone still suffering from this issue, especially if you're in Austin, TX where I can work with you (free) one...