Well, I have but due to an eating disorder.

Unintentional weight loss I'm sure you know can be a sign of medical complications, cancer, aides, malabsorption problems, malnutrition ect. When your dr's checked you for gastrointestinal problems do you know specifically what they looked for, tests, or anything. Do you have any other symptoms?

If you do have any other symptoms I'd keep pushing my dr to look farther. Gastrointestinal problems are not always easy to figure out. I'd be a bit concerned since you say you have a large appetite, as for the meds, I really don't know, I've only taken 2 from your list, Prozac gave me loss of appetite and Lamictal had zero effect on my weight or appetite.

Along with my eating disorder which is relatively under control I have malabsorption problems, doesn't matter what or how much I put in, I'm not absorbing enough of it, which has led to deficiencies, basically making a mess of me.