What are your ages?
Is today when you told him you wanted to end things?
What were the imporvements? do you mean imporvements just today?
Are you still intimate with him?
If he's showing a different side of himself and it seems like he may be working on changing the things that you don't like, then you might at least want to give him a chance and see how things go. Maybe you telling him that you wanted to end the relationship woke him up and he doesn't want to lose you. There's nothing wrong with giving him a chance, just keep in mind that it's not that easy for people to change, so its possible he could just be doing this to keep you. Time will tell more than anything else. I welcome your thoughts, let me know if you want to talk more