It appears that you may have a hiatal hernia in your diaphragm under your rib case. A hiatal hernia can develop when the esophagus passes through a small opening in the diaphragm that separates the chest cavity from the abdominal cavity. A portion of your stomach can slip into the open cavity and apply pressure on the opening. Acid from your stomach can move into your esophagus causing a burning sensation.When I had a hiatal hernia, I could feel the pressure of my stomach pushing against my diaphragm, and I would find with my fingers the point-of-entry in my diaphragm where the pressure was the greatest and push back to equalize the pressure. This tip was only temporary, but I lost 20 pounds, and the pressure and burning stopped. If you are able to lose weight, this may reduce the pain in your chest. If you lose weight and the pain continues, your doctor or a Gastroenterologist can place an endoscope into your throat and move through your esophagus and into your stomach to view the cause. Persons can be born with a hiatal hernia or develop it from lifting heavy objects. One or two bowel movements a week or two weeks may be caused by the hiatal hernia, or not. If you are constipated that prevents you from having daily or near-daily bowel movements, this condition also needs to be discussed with your doctor. Infrequent bowel movements can cause your bowels to become rock- hard and can damage or cut your rectum if forced out. A first-start might be to use a mineral-oil enema followed by a regular enema if you have problems with your bowels. The nausea you feel could be from the stomach acid affecting your esophagus and stomach.
Good luck with whatever decision you choose.
Harrald
While the lump and nausea could be GERD or hiatal hernia, the change in bowel habits and infrequency require a doctor visit to rule out a blockage. Try to find a good gastroenterologist.
John