this limiting belief can spawn from a few places. you need to get to the root of it. two of the places i can think its coming from is the possability that deep down, you dont feel you are worth anyone making changes for. for this you want to tell yourself that you are worth someone making changes and that you are amazing enough that someone will want to be with you no matter what. it can also come from past experiences, as you have pointed out he never has. both of these reason kind of go hand in hand. if you feel he has never fought for you, then you are also feeling that you arent worth it to him.
so then, ask yourself. is he really worth you fighting for? is he really worth you giving up your happiness right now to focus on him instead of you? are you fighting for the person? or are you fighting to get the feeling you got from that person? these are two separate issues. you dont need to answer that here, but be honest with yourself. if it is a feeling you are looking for, then remember, you are the one that controled that feeling in the first place. you can have that feeling on your own. and it is highly recommended to find that feeling on your own before you even attempt to get your ex back. with out doing that, chances are, even if they are to return, you will soon find yourself in the same boat.
remember that anything is possible. they once said man will never fly, and now look at us.
also, anyone looking to find a way to get to the root of what they are feeling i highly recommend reading The Sedona Method