I'm depressed and I have no reason?

For a while now I have been depressed. I self-injure and have constant thoughts of suicide. I'm a freshman in high school and ever since 4th grade I've had problems with eating disorders but they got more serious recently. I was bulimic and decided it wasn't doing anything so I starting skipping meals and lately I never feel hungry anymore. I just don't want to eat, ever. I started getting seriously depressed when my boyfriend, whom I loved (And don't tell me I didn't. I don't care what your thoughts on my love life are, you don't know what I feel) and still do, left me for my best friend. Nothing overly traumatic has happened in my life, while my friend who has been depressed also and has recently quit self injuring's father died, well her step father, but she thought of him as her dad. That's what really triggered it for her I think. She is at my house tonight, and she told me that she thinks I'm not depressed and I have no reason to be. She says nothing traumatic has happened and she doesn't understand why I hurt myself and why I hate my self. She says I have to real reasons. It makes me really upset and then more suicidal thoughts come along. I've been bullied for being fat before. I've also been called ugly quite my fair share of times. Even though most people tell me I'm not it really gets to me when people say those things. I get pressured for sex a lot by guys and end up giving in (but I am still a virgin, I just tell them I will) because I want to feel like I mean something to someone. So basically, I need advice. Whatever you have to say, say it.