Why don't you tell me which city you are in? There are many in Nanjing University of Chinese Medicine. I treated my stomach trouble there. I want to introduce you to a professor, Professor Guo Lizhong. He goes to Nanjing Qinhuai Hospital every Thursday morning and Jiangsu Provincial Hospital of Traditional Chinese Medicine in the afternoon. You can search his personal information online.
In fact, if there is a university of traditional Chinese medicine near a friend's home, just go directly.
Actually, I'm not in good health either. Some people are born thin and don't eat much. I am in my twenties, and my weight has been hovering between 40 kg and 50 kg since the third grade.
I wish your son a speedy recovery.