Have a breath test for Helycobacter pylori infection of the stomach. This causes bloating, burping, heartburn and posibly burning pain in the middle upper abdomen.
If you ever have right sided upper abdominal pain (under right rib cage), it may be your gallbladder. First test is ultrasound.
I advise to consult with a doctor for testing to find cause, I know when I have chest congestion or post nasal drip, I'm always clearing tons of clear mucus from my system, feel like I'm drowning in mucus sometimes. But get checked out by a doctor, for proper diagnoses and treatments.