This guy WILL NOT take a hint, what do i do?

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I've known this one guy since high school...i'm in my early 20's now. He's so annoying though! We aren't even close, we never hang out, and i haven't seen him in years but he's always all over me and he won't take a hint. He follows me on all social media, and will constantly text me over stupid stuff- for example something i tweet, just to give him an excuse to answer. He always tries to ask me out too!

It's gotten to the point where i am just annoyed. I dread seeing his name pop up. He tries to be nice, so if i post about having a bad day, he'll send me a funny picture or something- but it just comes off clingy. There have been times where i ignore his texts. When i do respond, i'm short with him, and he still does it. I am literally sending him all the signs to show i am NOT into him and he doesn't get it! Not to sound like a shallow b**ch but he's just not in my league and he acts like a psycho! One time when i ignored him, he ranted this giant post on facebook subliminally about me. Like TAKE A HINT!!!!