I lost my appetite while on Lexapro too, take that as a opportunity to create a healthy relationship with food. Have your 3 good meals a day even if you are not hungry. Once I got out of it my appetite came back and I was so used to not eating which made me eat compulsively and now Im fighting to lose weight.
I was the same way with BF, always hungry. Its weird when that hunger goes away! Make sure you're getting adequate protein in (minimum 60 grams, depends on your height/weight) and eat some healthy veggies and stuff when you do eat! Protein shakes are good for when you're not hungry, but need nutrients. I wouldn't eat when you're not hungry. In some people, they initially lose their appetite, and then it comes back, so watch for that.