Re: I'm being harassed by this kid, my ex's best friend, and I'm so stressed & misera
I agree with akazie. Just try to ignore him. I know it's harder than it sounds but people like that enjoy seeing how much stress they can cause others. so the more he sees how much he's getting under your skin the more he's going to do it. If you show him it doesn't affect you and you couldn't care less about him, then sooner or later he'll get bored, move on and stop harassing you.
(For example, think of a prank caller situation - if a prank caller called someone and that person didn't get angry or feel harassed in any way, there would be no excitement for the prank caller. The more angry the person on the other line is the more fun the prank caller has and keeps harassing them further. If the prank caller got little or no response, then he doesn't get any satisfaction and moves on to the next call victim)
If he's threatening to hurt you though, and you really feel that he actually will go through with it and do something to harm you, then you really should speak to someone with authority and describe the threats that he's making. you're much more mature than he is. good luck!