Re: stomach ulcer
When I had a stomach ulcer my symptoms were an awful pressure type pain (could be classed as Knawing) behind my bellybutton, terrible Nausea, and a regurgitating feeling after eating and belching. In my case I also bought up blood through my mouth but this dosent nessessarily happen.
I was sent for an Endoscopy that revealed I had had an Ulcer and also had H.Pylori. H.P will cause the same type of symptoms and is known to be the cause of Ulcers.
To diagnose what your symptoms might be, wether H.P or an Ulcer you would need an Endoscopy.
Hope you get an answer to your problem,