Why am i so afraid of physical conatact?

im 16 and i can not let anyone near me i do not like hugs i do not like shaking hands when ever someone Tries to touch me i become extremely uncomfortable and i have let out a blood curdling scream when someone has touched my thigh. i have never been molested or touched inappropriately i have social anxiety and general anxiety i am very selfconces what could this be a sign of just thinking about someone sitting near me can send me in to a full blown panic attack