Talk to Gastroenterologist on Giardiasis

My son is 3.2 yr old. He is having giardisis symtoms from 3 main trigger is traveling, after which he got severe diarrhea 2 times in 4 months time span. he is not having a peaceful is having a general feeling of illness and fatigue. i visited ped 4 days ago he gave zinc sulphate for 10 days [1] diatazox for 3 days [1+1] focin for 5 days [1+1] my son has lost 4 kgs in 3 months and not still okay even after having a good diet. he was dewormed with zentel and vermox what else can i do to make him feel like lactose intolerance is also absorved from 2 help me