I think some of it depends, too, on the type of carb. Starches, like potatoes and rice, turn to sugar quickly when you digest them. I think crackers and bread and cereal fall more into the complex carb category, which does not turn to sugar as fast.
You might want to look up "IBS diet" online. There's one out there that address what carbs you can have in moderation and which ones you're supposed to eliminate. Maybe it will help you.