Cancers, in general, do not produce gas and cause breathlessness at night unless you have concurrent obstructions in your intestine or lung-related diseases which is made worse by lying down. Bloating and breathlessness, on the other hand, are symptoms that do not lead to cancers by themselves.
From your description, you may be suffering from delay gastric emptying and reflux disease. These conditions tend to present with a sensation of a full stomach and periodic flow of gastric content back into the swallowing pipe. At times, chest discomfort or burning pain may develop due to acid injuries to the oesophagus. Some people may experience throat discomfort in the morning or cough at night.
if your symptoms do not improve with simple rest and smaller meal portions, you may need a proper evaluation from your digestive specialist to find out the exact cause and to exclude the remote possibility of a true stomach outflow obstruction with lung involvement.
Dr Quan