Malabsorption can be related to weight loss, fatigue, and diarrhea. I can t give you a probability if this is the correct diagnosis, but I can tell you that it is in the differential diagnosis for your symptoms. You don t say what the doctors checked you for, but if they haven t for this, it would be a good idea to get the work up. Sometimes a diagnosis of malabsorption is missed early on, so it s worth getting evaluated. You could in the meantime change your diet and see if this helps any. Avoid wheat and milk products to begin with. But get a work up for malabsorption. Hope this helps.