Lost84, play that tape through to the end in your head and be honest with yourself. Based on his previous actions and treatment of you....how do you REALLY think this will end? What makes you think this time would be any different?
Don't romanticize it in your mind...every second that you spend obsessing about this guy is time that you could be spending taking great care of yourself, working through your own issues, having a great time with your family and friends who love you, and maybe even meeting a nice guy who doesn't have a drug problem and who adores you!
Stay strong.