Probably, he knows how you are feeling.

Sometimes I know when I have nothing to give. I go into survival mode and admit to myself that I can't take care of anyone else. I just can't.

Most likely you, and he, are feeling this also.

Probably the best you can both do is give yourselves a break and not carry how you are feeling now, into the future. I am not saying that you shouldn't care, but please don't think that you are somehow failing during those times when you can't give of yourself.
It's temporary. And it will be okay. And you're doing perfectly by listening.