What Causes Pain In The Upper Abdomen?

Good Evening, I am scheduled to see my doctor in two days, however, I wanted to get a better sense of what might be causing my discomfort. I have periodic pain in my upper abdomen area. My exterior skin feels as though I have a burn, although there is no visible sign of any rash or anything like that. Then inside the area I get this pain almost as if I had internal bleeding. I have not seen any blood in my stool, it s just the sensation of something out of sorts. When I press on the area, the skin stays indented, just as if there is swelling. Any ideas? Thank you.