Wolfgal, the usual tests did not helped me too much. in fact 4 endoscopies did not find H.Pylori EVEN i have discovered later by stool test. so its not 100%. if you have H.pylori issue...
saying that your small intestine biopsy its clean it means they did culture or look for several bacteria not for every possible ones. and they are not spread all over maybe they missed the spot.
I did several stool tests for bacterial overgrowth which came back "clean". lately found out they checked for 3 maximum 4 type of bacteria but did not specify on the results that. two of them were from outside the body like Salmonella etc. Now, when i have a test i always ask "for what specific type of bacteria did you test my stool for?"
if you burp that means IMO infection in small intestine or stomach. it not just hpylori which can make you burp but indeed its more likely. some bacteria can increase your allergic reaction to almost everything including supplements.and yeast can do that too...keep searching!