Is stomach cancer rare of someone in their early thirties?

I'm going in on Monday for biopsies. My symptoms are beem upper abdominal pain, nausea, and vomiting. They originally thought that it was my gall bladder, but other tests have ruled that out. My doctor told me to prepare for this as a diagnosis. We had thought that it may be ulcers, but the doctor said that I would have had some instances of blood in my vomit (I know its gross). Should I be worried?