Can someone PLEASE help me overcome extreme shyness?

I have social anxiety disorder and talking to people is extremely scary for me. I don't like being known only as the quiet girl who never talks at school. I have few friends and don't trust any adults. I have no best friends. I am not allowed to have friends over and haven't since i was 10. My mom usually won't drive me to my friend's house if someone asks me to hang out, because she'll make excuses such as its too much work or you have to babysit, so i can go to a party with my friends. She goes out every saturday which means that i have to babysit my 5 younger brothers and sisters and one is autistic. Talking in cl gives me anxiety attacks. My attacks are usually hyper ventilating, freezing up, digging my nails into my arm or hand, shaking uncontrollably, and i will even fake sick just to avoid the situation. Talking scares me even to my parents because they aren't exactly people who would understand or care, and they don't even know i'm like this at school. Anything that draws attention to me scares me and one of my teachers won't understand, she is giving me a C in cl because i don't participate. I'm trying really hard but i'm too scared to talk. I try little things like giving people who sit next to me in cl a compliment but then at last second i get too scared and chicken out and then hate myself later for being so scared. Any suggestions?