Would appreciate some advice

This past week i have had zero appetite. I'm barely consuming 500 calories a day. I don't feel bad and I don't have trouble keeping anything down, I'm just not hungry. I don't crave food, and when I force myself to eat, it doesn't taste good and I feel stuffed because I wasn't hungry to begin with. The only thing I crave is water. I was supposed to have my first fill on oct 3rd but they denied me a fill because I lost 20 pounds in a month. They said that was to much. I have no fill, so it's not that. Is this the green zone or something else? I'm just now 6 weeks post op. Has anyone else experienced this and if so, how do u get your protein and calories in?