I'm not sure what is happening to me. I don't want to wake up in the morning. Everything feels like a dream; I'm struggling with school, I can't stand to look at myself in the mirror, I yell at my parents when they haven't done anything wrong, and I'm a totally different person when no one's around. I feel like my chest is being stood on when anyone talks to me. I'm trying to be "normal" but it's hard when I don't know what normal is.
When no one's around I smile more. I can have an intellectual conversation, even though I'm just talking to myself, but when I try to have a conversation with someone else I freak out. I literally make myself sick thinking about everything at once. My mind feels like it's going a million miles an hour no matter what. I'm getting really scared. If someone could explain what's happening or if this is normal it would be greatly appreciated.
There is no such thing as normal. You don't have to be like other people. It is all right to be like you - unless that causes you distress. It does, so you need to fix it. Also, I am sure how you've been doing things causes distress to other people who care for you, like your parents.
What you have described is not your nature, but a pattern of habits you don't like. So, you need to change them, and do things differently. This is possible, but much easier if you have a wise person to guide you.
You did a very good job of describing how you feel, but nothing about your circumstances or past. Without such detail, I cannot even start to suggest where you might look for the cause of your problems. You can ask yourself a few questions:
How long has this feeling been bothering you? When did it start? Did anything happen in your life at about that time, or not long before? Are there occasions when the problem is not as strong? Answers to such questions may help you to understand what's going on.
I strongly recommend that you have a few sessions with a good psychologist who works with teenagers. I don't know where you live. Some countries have free or subsidized access to psychologists. Even if that's not true for you, therapy can be an investment that will improve the rest of your life, so it's very worthwhile.
If your family cannot afford it, there may be free options. Your school may have a school counselor. Various charitable organizations offer free therapy. Many are religious, but they work with anyone regardless of religion.
I am happy to continue contact with you. Email me the answers to my questions, and we can do some detective work.