You're in quite a dilemma. You feel like you've had it. But six months is not six years. This relationship may be salvagable, and I get the sense that you are not really ready to walk.

I'm not a big believer in people's capacity to change. However, if your guy is really making an around-the-clock effort . . . and not just turning on the charm when he wants to get laid . . . then he may really want to work to save the relationship. Let him know that you won't continue in a relationship like the one that the two of you have had, but you aren't totally ready to chuck it. Praise the heck out of him for any new behavior that represents positive change. That doesn't mean you have to instantly become all lovey-dovey. Tell him you haven't, yet, regained trust in him and that it will take a while before you do, if you do.

If it turns out that the change into being Mr. Niceguy is superficial and you just can't regain the desire for closeness that you had before, then maybe you do need to end it.

You don't have to do anything, until you are ready. You don't have to end it now, but neither do you have to go back to being his enthusiastic lover. It's okay to decide that the relationship is in Limbo, and that you are putting off making a decision for now.