You are very perceptive in that you think the problem may lie with you. Not that it excuses any of his behaviour or that his behaviour is your fault, it is not. I think it is a matter of what type of men you are attracted to. I have seen it over and over in AA and Alanon. People who have no idea about eachother will be attracted to eachother and get together and every damn time it turns out they both came from an alcoholic home. One will be an alcoholic and the other co dependent on them. A very bizarre mysterious force at work. The women call it having a broken picker. I have experienced it myself. I am a rescuer. The night in shining armor who wants to rescue the damsel in distress. Consequentially I always end up with women on the rebound. Once they are over the previous relationship and are done using me as a band aid I get dumped. I have had my share of obsessing and spying on voice mails, emails, face book etc. I decided since my daughter was young that I would stay out of them and work on me. Now I would like to be in a relationship again and think I am healthier but the damn depression always seems to get in the way. That is another issue.

I would suggest taking the time to get over the obsessing, let yourself grieve the past relationship and get over the hurt, and then work on yourself. Melody Beatty at one time was the big expert on co dependency and I have read all her books. I am sure there are many more out there. It can take a long time but your awareness has you moving in the right direction in a very healthy way.