The reason for gas, weight loss, cramps, etc.

Could be eosinophilic gastroenteritis. Your doctor will often just call it
"irritable bowel syndrome," which is basically a way of getting rid of you,
and needless to say, not being of any help, as usual. If you have weight
loss following a "food-poisoning" like episode, it could eosinophilic
gastroenteritis. Often, this is found in third world countries, but with
people trying all kinds of things for "health reasons," it seems to be more
common in "civilized" nations. Be sure your doctor rules this out before
telling you to take drugs that mask symptoms but do not address the
underlying cause. If it's a bad case, they prescribe prednisone, which is
fine for a week or so, but it's important to determine why it is happening,
then eliminate the cause. Unfortunately, you will often become sensitive to
certain food proteins, and will likely need to eliminate them from your
diet.