Hello,
Before I can answer, I should say that the best person to talk to about this would be a doctor, a psychologist/psychiatrist, or an actual counselor (because most of us on TeenHelp, including myself, can't actually give a diagnosis of any disorder). That said, it sounds like as far as eating disorders go, what you describe doesn't seem to have any of the typical triggers that lead one to develop an eating disorder. I don't think you need to worry about your loss of appetite leading to an eating disorder, because it doesn't seem to be the case that you're avoiding eating due to a negative self-image, unhealthy perceptions of how you should look relative to what you actually look like, or other such issues.
Your appetite loss is still a serious side effect of depression, though, and if you have anyone in your life that you can trust and speak to about whatever issues have been bothering you, it would be a great idea to do so. School counselors, parents, family/relatives, friends, and teachers are great people to talk to. Sometimes having online resources like TeenHelp is useful too, but it doesn't compare to having someone in your life who you trust and to whom you can speak with about problems you're facing.
I hope I helped a little, feel free to
pm me if you'd like someone to talk to.
Best,
Tro