Hi there ~
Hair loss in eating disorders is very common. It is usual that all your testing, be it laboratory or imaging will turn out to be fine unless you also have binging as a symptom, which from you history does not seem to be the case. Visiting with a dermatologist
to find out what may be the cause of you hair fall
may be one way to go. Another way is to find out if you have any micronutrient
deficiencies. It may be a good idea to have supplements which are rich in zinc, it is found to be a good one for hair growth. Changing your antidepressant will also be a good idea since you have been on only one single antidepressant for your stress
. Eating disorders are tough to treat and distracting yourself while eating and eating your heart out and not thinking about it later is a good idea. I suggest that you visit with an eating disorder specialist to deal with your problems. Being all that you are and being a pre-med student is stressful. I hope you are also enjoying life by doing other activities that have always made you happy.
I hope this helps.
Take care and have a lovely day !