Thank you for the query.
As all mentioned tests are negative, anxiety can be your main issue. This can trigger stomach acid secretion (what gives chest burning), fast eating and swallowing the air (what causes burping) and disturb large intestine (causing constipation
Other possible reasons of burping and stomach bloating
are chewing gum, smoking, loose dentures, drinking carbonated drinks.
I suggest you to consult your doctor and consider anti anxiety treatment (SSRI medicines). You should avoid coffee, coke, alcohol. Please start also probiotic
supplementation and Magnesium
400 mg once a day.
Hope this will help.