I don't think it's wrong to not want to tell him right away - I think it's fair to say, "I'm currently separated, but I won't bore you with the gory details just yet" or something - so he knows a) you're not divorced, b) the details are a little gory, and c) you'd be fine with talking more about it, just not yet.

Does that make sense?

H: 39, Me: 37
SD: 18, S: 7
M: 9, T: 10
"I love you but am not in love with you" - 5/11
Discovered online affair - 7/11