What does an ulcer feel like?

For the last year I have had these episodes off and on where my stomach has this gnawing burn. Nothing phases it. I've tried antacids, food, pepto...It will strike for a few weeks (it's always worse at night) and then disappear again. I said something to my mom about it and she thought it may be an ulcer. I guess my dad used to have them. Does this sound like an ulcer? How do they diagnose an ulcer?