My abdomen hurts when I jump or sometimes bend down, is that serious?

Why abdominal pain? There are lots of reasons for abdominal discomfort, and not all of them are due to the GI tract. Even "functional" syndromes may be present without underlying "disease." if pain with meals consider peptic (acid), biliary, or pancreatic disease. If bleeding or tenderness is present, this suggests inflammation, ischemia, or infection. Exquisite tenderness is quite concerning. Please see your doctor.