To clarify, I don't tell DH absolutely EVERYthing automatically as a matter of course (nor did I say I would), nor do I feel that I must share every little intimacy with DH (partly because half of it would bore him to death), I just wouldn't expect anyone in a long term relationship to keep a secret from their partner. I wouldn't want to put anyone in the position of having to watch their words with their partner. I don't think it's fair.
I don't tell DH things that he won't care about, and that aren't bothering me at all. However, if there is a need to discuss in that a secret is bothering me/I'm not sure what to do about it, then it's natural that I would want to discuss with DH.
E.g. I told one half of a partnership that I was pregnant before we were 'officially' telling anyone, and I said we weren't telling people yet for the usual reasons, but I assumed as a matter of course that she would tell her DH. No way would I expect her to not tell him (if she wanted to) or to be being 'careful' about what she said to him (say if e.g. they were discussing whether or not we or anyone else was likey to have kids soon), no way would I expect her to 'watch her words' with her DH. Similarly I told a male friend (I'm also friends with his DW separately from the two of them as a couple, but hadn't got around to telling her yet) and no way would I expect him not to tell her, in fact I got a very excited phone call from her about 3 minutes after I had spoken to him. Again, no way would I expect him to watch what he said to his wife in their own home.
If that makes me weird, so be it, but I honestly think that it's weirder to keep secrets from your DH.
In ref to the OP though, she should never have agreed not to tell him, then big old fat gone and done it anyway.
D