I think these^ would be like slapping a band-aid on the problem.
Your best bet it to figure out why your body is reacting the way that it is. If you eat 2 servings of peanut butter on your sandwich you are looking at 30 grams of fat. Should the human body be unable to digest 30 grams of fat(if you have a gall bladder of course) or is that a symptom of other problems?
My first hunch would be that you are on a diet in which you have become accustomed to eating only a handful of different foods every day. The PB sandwich is like the digestive curve-ball you throw in every week. Do the elimination method I wrote above and see how you react. If you react poorly on all three sandwiches you will know its a sensitivity to variety and the way to cure that is to have more variety in your diet. You can also try an optional low-fat peanut butter sandwich and see if it is fat. But again if you can't digest 30 grams of fat that is a symptom of other problems.