Help? People who know about mental health.?

Okay, so I was at my school library and I found a book on shyyness and, because I'm extremely shy, I decided to check it out. I read the signs of being a psycosomatic and the withdrawn shy person part matched me completely right. When I was younger I hated being in team sports, I skipped recess to stay in class and if the teacher kicked me out, I'd go to the library or read in the halls. I also preferred to stay alone with nothing but rock music turned up really loud, painting and drawing tools, and books. I always played board games by myself and I've always hated being outside. At first I just thought I was lazy. I've always done my homework, obeyed everyone, got my way through flattery and since like sixth grade ( last year) I've hidden my emotions. When I want to cry, I don't. I wait until I'm alone and then just let the misery eat me. When I'm angry, I imagine bad things or think bad things. I'm never truly genuinely happy and I almost never smile. Since last year, I've obsessed over how I look and I usually call myself ugly or fat, cause I am. Ever since I started seventh grade this year, I hate walking in wide open and largely populated spaces( like class and the cafeteria) and I feel like everyone is staring at me, judging me, criticising me, whispering about me. It makes me feel uncomfortable. It's gotten so bad, I don't even like going outside anymore. I hate being looked or stared at, being touched in any way, and I hate having my legs or arms bear. I always wear black or another dark color, and I'm always wearing a black sweater. I get headaches and I have asthma, I have a bad heart, and I don't participate in P.E because I'm scared that everyone will watch me and say " look at that fat ugly girl running around." It makes me anxious and nervous just thinking about going outside. I'm usually sad for no reason and I write disturbing stories that my teacher say are wonderful. I usually paint or draw in black and white, spending hours on art and then just ripping it up because its not good enough. I don't evn know who the hell I am. If the popular kids talk to me, I act cool and snobby, if I'm with hyperish and upbeat people, I'm hyper too. If I'm with calm quiet people, I'm like that too. I adjust myself depending on the mood of whoever I'm talking to at the moment. If I dont act like them and I act what you could describe as emoish. I love the concept of death and yet, I also like faeries and romance. I practically hyperventilate thinking about wearing shorts or even leaving my room. I prefer to talk to adults than kids my own age and speak formally, as if I was born in the seventeenth century. I get pushed around and I dont defend myself. I just glare and let it happen cause I think " It'll just happen again" and it does. I'm pretty short, not like thats a problem, but combined with the fact that I'm usually carrying like six books a day and glaring doesn't exactly help. I hate smiling or laughing and I'm usually rude to my friends. I can't help it. Lately, my grades have dropped and I've been feeling like "What's the use" and " What's the point." I think of things like " What's the point in life". I've never tried killing myself, but I have thought of it. I'm just to scared to try. There's more, but this is already really long, so I'll stop. Please tell me what's wrong with me. : ( I'm alos usually twitchy and suspicious of any one who comes near me, especially boys. I don't trust very easily and I always cover my mouth when I talk.