You sound like my son(16). he could be starving (quite literally) and unable to eat more than a mouthful or two (he was weighing under 98lb) From what I understand the inflammation stops the body from digesting/absorbing nutrients and in my son's case (he not one to sufffer with diahorreah(sp?) his system was completely backed up and it was physically impossible for him to swallow any more food and then his appetie just deteriorated.
He was put on various drugs and approximately 7 weeks of total enteral feeding (basically partly digested food drinks) and then solid food re-introduced over 3 weeks. This has done wonders for him, colour has returned to his skin and he is now gaining weight
He still cannot eat 'normal' sized meals but has lots little and often as well as continuing on one of the enteral drinks and a high calorie shake drink every day in addition to normal food.
Tell them (politely ) that they are ignorant about the disease (as I was-although I did appreciate something was drastically wrong, just didn't know what) That it is not simply bad stomach pains and typically diahorreah, and it can cause a whole host of other issues, inflammation, strictures, bodies inability to absorb /digest food/nutrients resulting in anaemia and malnutrition, fatigue, loss of appetite, mouth ulcers, painful joints and all kinds of other problems that I have failed to mention.
Have you seen a specialist for help?