I don't believe in dating while M. It has never been an option for me although I know beyond a shadow of a doubt that my H would be devastated by that.
Neither do I. Moral issue for me and for the reasons stated earlier.
Now, that said, there's nothing worng with him having the belief you ARE dating. Which is where being mysterious comes in. But, one thing Sandi told me early on was not to lie. Being vague is not lying.
