Hi, Welcome to Health care magic forum.
                   As you describe, you can try to gain weight. 
                   Use plenty of calories, fats, and 
proteins, medically you can use the the injections. 
                   So i advise you to consult a physician for diagnosis and treatment. 
                   I usually prescribe to my patient with such symptoms injections of anabolic 
steroids periodically. enzyme preparations, and 
protein supplements.
                   Take more of green leafy vegetables, pulses, sprouts, and protein rich foods, to have a good health and weight.   
                   Wishing for a quick and complete recovery. Thank you.