Why does pancake makes my stomach upset?

Sugar: Pancakes are nearly all sugar calories. That is where i would start.

Several possibilitie: Assuming you're not allergic to wheat, i wonder if it could be what you're putting on the pancakes. If you're putting a lot of thick syrup on the pancakes, you're getting a large osmotic density ( a lot of molecules in a small amount of volume) which can suck water out of body tissue (the stomach). If you're not been drinking much water as you eat, you may want to try more water and less pancake.