Every single thing you've described I have been through as well. The worst is probably not being able to eat because you lose all energy and motivation and basically feel sick. My best advice would be to see a professional, at least see a therapist. For most people, highschool is hard. Most adults will tell you that after you graduate, things will start to get easier. I personally know someone that had severe anxiety and depression throughout high school and now she's in college with barely any problems. Since you're still young and have a few more years to go, try to seek help to get you through. Also, when you are unable to eat it's helpful to drink something like a protein shake or an Ensure. It gets something in your stomach and you don't have to chew. Try to do activities that you know will make you happy (if any). I used to love drawing, watching anime and playing video games. Now the only thing I find enjoyable is going to the mall and buying a ton of new clothes that I'll probably never wear. I know that sounds ridiculous, but when you're suffering with depression, anything that could make you happy helps. If you ever need someone to talk to or discuss this further, feel free to message me. I'm not an expert but sometimes it helps to have someone to talk to.
I believe you should talk to someone, like a therapist. To vent or to discover what's going on.