I like my best friend but have i blew it?

He asked me out when we just met but i rejected him because i already had a boyfriend. Now i don't and i think i really like him. He's always calling me and texting me to come over and stuff to play the xbox or watch 300 or play cricket or something. Nothing actually romantic. He treats me just like one of the guys if you know what i mean? I get on with his friends quite well too and they're always joking about us being together or whatever. He's always making fun of me for everything and i do the same with him. it's pretty much how we communicate. He texts me late into the night saying he can't sleep and stuff but he hasnt made a move and I've been single for almost a month now. Does he think of me as just a friend now? And what should i do?