What's wrong with me? I feel like S***?

Well this started happening about like Sunday. I was actually sick that day, and I was suppose to go to my cousins house for her going away party. I couldn't make it, and I felt like s*** ever since. I told her I would make it up to her and I did, she's crazy about these bracelets called something like Alex and Ani I believe, so I bought her one. I thought maybe making her happy would make me feel better. But I don't feel any different. I stopped eating, I won't play video games anymore (and I am a big gamer), and I been to nice. Nice enough to let people like walk all over me. I also been extremely sad and I'm filled with all sorts of emotions. But everything is leaving me, the only thing that now comforts me is my friends. No one knows I feel like this, my parents noticed my rapid change in diet, and how I'm being much nicer and calmer. But in the inside I am like crying and I'm just holding in all in. I don't know what's wrong with me. I hate this feeling and I'm in pain for not eating enough. I feel weaker and weaker and I just want this to stop. I feel like Everything that made me who I am is just leaving me. I feel weaker and I just, I just want this to stop. I shouldn't be like this, right? I mean I'm only 15, and I just feel broken. I can't sleep as much as I use to. My emotions and sad thoughts keep me awake. The only hope I feel is when I'm actually asleep and I'm dreaming. I mean I don't feel like this in my dreams. In my dreams I'm much more calmer then I am in reality, even if its like a nightmare or something. I don't know what's wrong, and I need someone's help please. I really don't want to go to anyone I know in real life.