Huge Backslide After Affair Recovery

[hopeOK]

My H is concerned about me stabbing him in the back again... saying hurtful things about him behind his back. This is what he said-

"That is part of what I struggle with, I don't know if it's better to know about it so that I can get myself into thinking that I can keep you from doing it anymore. or if it would be better not to know about it and then have you continue to do it without me knowing.I know there are plenty of other people that you could have already told. and plenty of people that you could still be talking about me with."

So what can I say to this? I want to make sure I am saying the right thing that is supportive... I have already said too much that makes him get defensive or start attacking me again.

Here is what I was thinking-
"I see what you are saying & I can see how that would be a difficult thing to figure out. I know I haven't been trustworthy so you cannot believe what I say. I don't really know the answer to this other than what I have already done & that is to say my accounts are open to you. But it is just like you told me with O if you really wanted to talk to her, you could figure out a way. So I guess this is the same. If I really wanted to continue to say hurtful things, I could still do it. So all I can say is that I want to do better, I want to be able to bring stuff to you in a healthy way instead of dealing with things in unhealthy ways, and I don't want to be the cause of your pain again. I don't have any answers other than that but am willing to do whatever I need to do to help you feel secure if you think of anything. "