Thank you for all your kind replies. I really appreciate them.
I'm reading through the links (and the book).
I now realise that I have been doing all the wrong things over the past two and a half years. And it's lead to my husband walking out, and now saying that he wants to separate.
He seems confused though. His actions and words aren't totally matching up. I don't think he really knows what he wants.
Anyway, to save my own sanity, I've been keeping him at arm's length. I've always answered his calls, texted him, helped him out. But now I've stopped, because I felt like I was getting completely mangled in this whole thing. I felt like I was drowning.