Is Stomach Cancer Hereditary?

My grandmother passed away from stomach cancer three years ago. I remember her going to live with my parents, and for a long time they passed it off as her being lonely. My grandfather died from Alzheimer’s a year before she was diagnosed with stomach cancer. When I visited my parents I noticed that after meals my grandmother was nauseated. She had stomach pain, bloating, nausea.

So recently my digestive system and I are not getting along. I have an appointment with a specialist the 21st of this month. But, every day that I struggle with nausea after eating, or upper abdominal pain, and upper back pain, diarrhea, or constipation followed by it. I'm fatigued. My blood pressure is low (though might not be related). I had a very short week long flare up of this in January and the doctor I saw at a very busy family center in a hospital just brushed it off as nothing. But, then a week later I had this terrible excruciating stomach pain after eating and he told me it was an ulcer and I should take antacids for a month. Well a week or so into June I started having nausea. Then the stomach pain. Now it’s every day, or every other day and the symptoms don't always happen at the same time. One day I may be too nauseated to think about food, and the next day I may have stomach pain. Then, the next day I may have back pain. I saw another doctor, told them that I was on medicine for an ulcer a few months ago. She didn't run any tests. She just said, "Oh, well, it probably didn't fix it. Take three months of it." Last time my symptoms cleared up after two days on the medicine. It’s been a month and things are getting worst. Instead of every three days, it’s almost every day. 

Anyway, after a long winded explanation of my problems I just want to admit that I'm a little afraid, because I see my symptoms mimicking my grandmothers before the family finally couldn't hide her cancer anymore. I'm just wondering if it is hereditary. Or am I getting overly anxious? I mean, I know there are a whole host of things that can go wrong with the digestive track. It could be gallbladder, pancreatitis (though I'm not an alcoholic but both my parents were). 

Two terrible things run in my family. Cancer and Alzheimer’s. My uncle had throat cancer that turned into lung cancer that moved to his brain. My cousin had breast cancer, but survived. My grandmother had stomach cancer. My grandfather on my father’s side died of colon cancer in his early 40’s just after my dad turned 18. That’s just my immediate family. So, needless to say I’m hyper sensitive to the idea of cancer, because genetically I’m probably susceptible to it.

 

If anyone who has had stomach cancer or who knows someone who has had it, could you offer me insight into it or maybe help me dispel the anxiety over having it. It’s just every day I’m sick I worry more and think about my grandmother’s last days.