Please help, very important!

I’m 18 and was told i am severely malnourished for my height and weight. i’m 5’7 and 102 currently. Last year i had over 10 surgeries and i think that has contributed to my weight loss as i used to be 135 lbs in january 2018. i have lost 30 lbs and go to the doctor every month and have been for about a year now. They have me drinking boost plus for extra calories but nothing is working to help me gain any weight. Any help is appreciated!