I have had this problem also. I burp CONSTANTLY and big disgusting truck driver burps. My boyfriend gets so disgusted but I cannot help it! I have to get it out or it will feel trapped. It's terrible.
Anyway, I have started taking dairy free, soy free and gluten free digestive enzymes (plant based) and it seems to have helped a bit. I've only taken them for like a day so the belching isn't completely gone but I do feel less gasy. I would give it a try. They are all natural and also assist in digesting good (which also helps with GERD.)
Gas X is like over the counter stuff. I wouldn't really want to continue taking that every day. I'd really try something all natural that can assist your body in the real problem: digestion. Not digesting your food properly can cause excess gas - which leads to burping. Gas X is just killing off gas. Not really getting to the route of the issue. See what I'm saying?
Burping can be caused by GERD - but it sounds to me like trapped air. When we eat we sometimes swallow air especially if we talk while we are eating. Also if we are drinking a beverage during the meal, we can swallow air. Some people wait until they are finished eating to drink their beverage.
I suggest that you buy some simethicone. Gas X or Gas Relief from your drug store. They look like Tums but don't contain calcium.
Hope this info was helpful. Wishing you the best