Okay hey I'm new to this site to and I'd just like to say - ignore the people at your school. I hope you don't care about what they say about you.
I was in a relationship with a guy like you, and I broke up with him during middle school; when high school started he turned into a different person and started saying all this shit behind my back. A lot of people I knew started talking shit about me too; thinking I was a bad person. At first, I started feeling angry and bad and slowly, my best friend started turning her back on me. She began to hang with my ex and started smoking marijuana to fit with the "cool" people. My parents fought all the time and my older sibling never talked to me. I slipped into depression and well almost dropped out of school, but mainly I understand how you feel to be depressed.
I know being positive is hard and feels ultimately futile to get to, but trust me, you have to try. Instead of thinking about how bad your life is, or your ex - think about things you can do instead. Occupy yourself and go jogging or open a word document on your computer and write a story; let your mind flow.
When I was depressed, I would listen to music and get on my feet and DO something, even if it was stupid. I found a passion in writing and would randomly take the bus around the island to see something, anything (I live on Oahu). It really does help. I don't know whether you'll even listen though cause, this is the internet and I don't know you; you don't know me and most time to tell you the truth, advice over the internet sounds stupid, but I think this will really help a lot of depressed people.
Luckily for me, I got out of depression and even though I'm still struggling with other little problems, I over-all love my life. You've got to embrace yourself and just accept some things.
Like you said, you don't know who you are anymore, that happens. When I was depressed, I was so confused that nothing make any sense to me. I didn't know whether this or that would help me, I didn't know what made me happy or sad, I didn't know what I liked and what I didn't; I wanted to ignore my parents and everything they said, and didn't want to see my friends because I always tried to act happy for them. Soon it seemed like I was living for other people's happiness. I didn't know what to do with my life and where to turn to. Things seemed hard to do, like you said. Fortunately, I didn't cut myself but when I was alone I would throw tantrums. I really don't know what will help you because I could have a whole different whole outlook on your depression, but I hope this helped and if you want, you can message me somehow, lol sorry I don't even know how you would message me on this thing, like I said, I'm new to this thing to. ttyl