i’m losing weight on elvanse

Hello! Just wanna ask what is this, ive been taking my 30mg elvanse now for almost a month and I still cannot eat, i literally cannot get myself to do it… My pharmasist said that It will settle when I’ve taken it for a while but when. I used to take 40mg and we went down to 30mg. Now i weight 105lbs and I’m 19 years old 5’8. I don’t wanna lose anymore but cannot live without this med, I am so hopeless…