That's interesting. That's a hard one to tell you what you could do. I'm glad that you have a doctor reviewing this for you, to make sure that you don't have any other health problems that could be causing that condition.
There are numerous herbs that reportedly are known as appetite stimulants. I don't know if these work and can't recommend them as I haven't tried them myself, but you could research it and see for yourself. I have used herbs successfully for other health reasons.
You could look at alfalfa, angelica root, chamomile, hops, and horseradish. Chamomile is also commonly used for colds, upset stomach, and menstrual cramps. Before using herbs, I would do a lot of research on it. You can find some mild herbs that are packaged in tea bags at a food market, if you wanted at first. Later, you can see if making your own herbal teas from bulk herbs is something that you might want to do too.
I think eating lots of healthy natural (non-processed) foods is best. I don't know if that would help your appetite, but eating correctly I think is important overall for our health.