What Causes Upper Abdominal Discomfort, Bloating, Heartburn And Frequent Burping?

The symptom check for WebMD is not displaying correctly, so I thank you for the chance to ask. Since August, I ve been having upper abdominal discomfort, particularly after eating: a feeling of fullness/bloating, heartburn, small bulge above navel, frequent burping, trouble sleeping because of these. Have been self-treating with Tums and ranitidine (300 mg at night) but not improving. Brought on by forced inactivity while being treated for bladder cancer, and subsequent weight gain. Suggestions?