Dear thanks for the question.
I share your concerns. If I were your family doctor I would have advised you to try diet modifications than going for medications to gain weight. Following
diet plan will help you in your efforts
1 increase protein intake (milk products, egg, meat)
2 increase energy intake (cereals like wheat, rice, maize)
3 increase fruits and vegetables intake.
4 increase quantity of food intake
5 increase frequency of food intake (take something every 2 hours)
6 take plenty of water
This diet plan will take care of your weight, shine of face and general health.
Since you are recovering from illness this plan will help you. Follow it for 3 months.
I hope i have clarified your queries. Do write for follow up queries. Please rate the reply. I wish you good health. Thank you.