I think you should get a second opinion. While IBS is possible, you probably need more work-up first. This is because IBS is a diagnosis of exclusion, meaning that all other things must come back negative before we can say for sure that this is what it is. A colonoscopy
and endoscopy are great starts of this work-up, but are not complete. These two are unable see masses outside of the bowel itself which could be causing your feelings of fullness and lack of appetite. Gall bladder stones which can be seen on ultrasound
cause pain in right-upper abdomen which is worse after you eat and can be worse at night as well. This is the first thing I would want to rule out before giving you a diagnosis of IBS
I should note that the lack of diarrhea and constipation does not completely rule out IBS. IBS can manifest as just abdominal discomfort.
I suggest that you schedule an appointment with a different internal medicine doctor
. He or she can take a more detailed history of your symptoms, perform a thorough physical exam, and take a look at the results of your work-up so far. If you have not had an abdominal CT scan or abdominal ultrasound, then you will likely need one or both of these done to look for any masses in the abdomen or gall stones which could help explain your symptoms. In addition basic blood work to look at your liver function and pancreatic function would be helpful. Good luck.