When i finish eat anything i want to burp but i cant. insteated i pass gas.....what is the problem?

Not burping: This sounds like a mechanical problem. When you swallow air or gas, or your body produces air or gas from digestion (as with high fiber diets), there are only 2 ways to come out--the mouth or the anus. There is a sphincter muscle between the stomach and esophagus which, if tight, can reduce the ability to burp. In such a case, the gas has no choice but to move down the intestine as a fart.