so I went to do a read up on stomach ulcers over at wikipedia.
Symptoms
abdominal pain, classically epigastric with severity relating to mealtimes, after around 3 hours of taking a meal (duodenal ulcers are classically relieved by food, while gastric ulcers are exacerbated by it);
bloating and abdominal fullness;
waterbrash (rush of saliva after an episode of regurgitation to dilute the acid in esophagus);
nausea, and lots of vomiting;
loss of appetite and weight loss;
hematemesis (vomiting of blood); this can occur due to bleeding directly from a gastric ulcer, or from damage to the esophagus from severe/continuing vomiting.
melena (tarry, foul-smelling feces due to oxidized iron from hemoglobin);
rarely, an ulcer can lead to a gastric or duodenal perforation. This is extremely painful and requires immediate surgery.
from what I can tell on the rest of the article, they caused by bacteria in 80% of cases.