I have pretty much the exact same symptoms. I cannot burp either, instead I get these weird hiccup things. I usually take a combination of 150mg Zantac with maximum strentgh Gas-X, and that helps just a little bit.
But Sometimes the gagging feeling is just too strong, but for me, it helps if I sit upright with my knees up by my chest, and rest my head on my knees. That position seems to take some of the pressure out of my throat, and usually within an hour or so I'll start to feel better. I will also take small sips of water and that usually helps a little bit.
I posted a similar topic a few weeks ago, and a member named Harry listed some different supplements to try for help, but I wasn't able to get back on the forums to get the info again, so maybe he'll post them up again for us
Hope I helped you out a little bit.