how do you stop loving someone who treats you bad?

Nine years on and off, nine months off, then he talks of marriage followed by "let's go slow" -- that's got to be hard on you.  How to set limits with people who have some good qualities is tough, but if you don't do it then you get played hot and cold like this.  I think the answer has something to do with self-respect inside you, maybe fear nothing better will come along -- I'm totally guessing on this and I may be way off base.  I hope he hasn't been saying "let's get back together" as an excuse to have sex with you and then put you aside after that.  Try this:  check out a book like "Codependent No More" or "The Dance of Intimacy" and see if you find yourself in those pages.  The very fact that you wrote this note says you know you deverve better than what you are getting. 

Some guys just aren't ready to commit. That doesn't make them bad people, just that you two are in differrent places in life. In anwer to your question, you DON'T stop loving them (if you love him, you love him), but love is only one component of making a relationship work. Other components include commitment and compatibility. So, try to separate out your feelings of love from what would be best for you. Think of it as heroin so some other drug. Just because it feels good and gives you pleasure, doesn't mean you should keep on using it, and it certainly doesn't mean it is good for you!