Hi dear it is serious issue if you lost weight so drastically. I would recommend go for complete
health checkup for the diagnosis. There may be some underlying health issue which has resulted in loss of weight and appetite.
Next Steps
Post
health checkup diet Cam me modify according to the results. kindly visit the Dietitian after the check up for proper detail diet chart.
Health Tips
Till you get check up you can have frequent meals so that you get energy in some interval. eat what ever you feel like eating at point that may help you to increase your appetite and diet.
Just avoid outside food as much as possible.
eat more of milk and it's products, non veg, fruita and juices, and milkshake.