Help ? He acts obsessed ?

So I met this guy about four months ago, we exchanged numbers because we wanted to be FRIENDS, and we got kinda close. I have a boyfriend, he's single but he likes someone I know, and we're both "bestfriends". He's ALWAYS in my business. If I post something on twitter like "**** this." I get a text from him 5 seconds later "what's wrong bestfriend?" I usually say "nothing it's fine" and he's like "No. Tell me. I'm not leaving you." I mean, that's great, he's a good friend, but it's almost obsessive. He gets my tweets sent to his phone, he gets my facebook statuses sent to his phone.. I'll post something like "mallll (:" before I go to the mall and then he'll be texting me "So you're at the mall? I should come see you" when I didn't even tell him I'm at the mall. And if I don't text him back for like 30 minutes, he'll send me another text "It makes me sad when you don't text me back :( What else could you possibly be doing?" And I even tried completely distancing myself from him, one-word texts, sometimes not even talking to him at all because it's freaking annoying, and HE'S STILL HERE AND MORE ANNOYING THAN EVER. He's always on some sort of bullcrap like "you're changing. this isn't you." Like he knows me better than I know myself? Wtf is up with this kid? Why does he act like this and what should I do? I already blocked him on twitter.