Why am i so scared of everything?

ok so pretty much my whole life I've been scared of things like new people, the night, being alone, death, etc. from the time that i was a little kid, i never wanted to leave my moms side. i remember crying when i wasn't with her. starting school was one of the scariest things for me. i would always be so sad, quiet, i felt lonely, i was very very shy, and would sometimes cry during nap time. there was a time that i was so scared of death. i was five when my great grandma died and i would often sleep with all the lights on in my room just hoping she'd come back and that i don't lose anyone else. the thought of losing someone would always start my tears. i had lived in los angeles for a long time and when i was like in the third grade we moved to a city in san bernardino and i remember i only had one friend for the longest time because i was just so scared of any other person who'd come up to me. the other time i moved, it was just schools not city, i would spend all my recesses and lunch in the restroom just waiting for the day to end. it's not like people were mean, i was the new girl that everyone wanted to be friends with, (you know how it is when your a kid and theres a new student). i don't know why i'm so shy and insecure and sensitive, i know i shouldn't be but i can't help it. there was a time in the seventh grade that i would cut myself, it just made me feel good even though i knew it shouldn't. i stopped after a while. well now im in high school and for a while i began to get over it and not be as scared, but then my little sister lost her 11-year-old friend to a car accident and it really got me thinking. it's bringing back all my fears again. the only person i had lost was my great grandma, and that was ten years ago. and when i had first heard of my sisters friend, even though i didn't even know the little girl, it took me longer to get over than it did to my sister. so now i'm begging to be scared of everything again. please help me out.