I have sudden stomach pain with onset about 20 minutes after eating lunch. I had crab salad with seaweed. It started at the top of my stomach and moved down to the lower abdomen after about an hour of lying down on one side. Pain subsided but then increased when I took milk of magnesium (about 1 tablespoon). I had sharp cramping pain and nausea, no vomiting. My stomach has been feeling sensitive for a few days, but nothing acute nor significant enough to impact eating, for the past 5 days after having a flu shot. I have no chronic illness, am in excellent health, normal weight and exercise daily. It is rare for me to have this type of pain. As long as I lie still there is no pain, but I get nauseous when I try to get up. It has been 4 hours since onset and it is improved. What is going on and should I have something to eat?