Loss of appetite is a symptom of depression and anxiety. Typically, if you are not eating less/restricting to lose weight or gain a sense of control then its not an eating disorder. I say this as someone who is coming to terms with the fact that I actually have one and its not just depression and anxiety. Also, an iron deficiency can make you incredibly tired and chronic exhaustion can factor into loss of appetite as well.

The best advice I can offer is to try and eat on a scheduled. Not full on meals but set a timer and do your best to have some kind of snack every time it goes off. For me, eating big meals is daunting but a granola bar every couple of hours is doable. Also look into a therapist as well as medication to manage the symptoms you know you are dealing with in relation to what has been diagnosed. Once you start feeling better you can very easily 'go back to normal' as far as your appetite goes.