I have wanted to apologize to you for three years, but I have no idea how to do it without breaking you further. I was the worst girlfriend in the world. I lived with you and your friends for free, but came home every day and holed up alone in our bedroom instead of interacting with you. You and your roommates were incredibly generous letting me live with you like that, eating your food and smoking your weed, and I repaid you by treating you like shit, slamming doors and crying all the time.
This is the hardest part: I cheated on you with two different guys, both of whom I was convinced would save me from what I deemed a nightmare relationship with you. I was convinced that you were a neglectful asshole simply because you reacted with appropriate anger and mystification to my bizarre antics, which gave me the idea that I was justified in treating you so awfully for so long. I'm sorry.
You tried so hard to help me when you heard me vomiting up the food you cooked for me every night. You had no idea how to handle my growing eating disorder, but you tried your hardest. Yes, I was psychotically depressed at the time, but there's no excuse for behavior like that. It has been three years since I was hospitalized, effectively ending our relationship. I'm still in therapy for the eating disorder and the depression and the anxiety. I just wanted to say, albeit anonymously, that I will be sorry for the rest of my life about the hell I put you through. You're a wonderful guy and deserve the very best that some healthy girl can give to you. Hopefully, someday I'll be able to apologize to you in person.