Facebook danger

Hello,
my prob is the next

theres some one, getting into my account and changing my pasword it dont matter how manny times i change it the go right away and change it, the have created facke accounts wit only me as a friend and send me treghtfull msgsss, they stole private picts i had and telling me to chek porn websites that they have posted them, they also sayed they still have them and that they might post them again, the thing is i have deleted all of the accounts i had, the pictures from my pc and im really frustrated, i would like to know if with the msgs they sent me i could find out where it came from, please i need help!!!!