I appreciate your post about the need to eat and maintain your weight. I also work to keep my weight up. I've had three surgeries of the upper digestive tract which included resections. After the second surgery, I also experienced a diminished appetite with weight loss. it was a concern to me as well. I suppose whenever we feel any part of our life is out of our control, it has a way of creating anxiety.
Since you mentioned having seen an endocrinologist and a dietician I'm wondering if you have seen a gastroenterologist. This doctor might do endoscopies to look for any problems in the digestive tract which may cause weight loss or a lack of appetite. Have you seen a GI specialist recently?
While it is certainly difficult to eat when you don't feel hungry, I certainly agree with what Sue, @sueinmn, said about being very intentional about eating small meals on a regular basis. Meals and snacks high in protein and good carbohydrates are important.
I look forward to hearing how you are doing with this problem. Will you post again and keep in touch?