leave...

I have an ex that I can not get over. As much as I want to.. he wont let me.
We have been broke up for 2 years now! We do have a child together and we were only together for 1 1/2 yrs. I am trying so hard to walk away from him... to move on.. but he doesnt want me to.. yet he doesnt really want to be with me either.
I try and talk to him about it... and he just kinda blows the whole conversation off like i am just crazy.period.
Once again- now he wants me back... and even tho i love him with my whole heart... i dont think i want to be with him. he's not a happy person, and he brings me down with him... He's very negative... and over all is not happy... and really doesnt make me happy...
So why cant i just walk away? Why do I have such a hard time ignoring him?
I want love. I want friendship. I want happiness...
and as much as I long for those things...this man can't provide me with them.