When is it "nothing"?

Why is it i get the feeling that there is always something wrong when i ask someone "What's wrong?" and they reply, "Nothing."

But then again, i might be completely perasan - perhaps, "nothing" really means "nothing" as in "everything is ok, therefore nothing is wrong."

But, its been my unfortunate experience (with women mostly, i'm afraid to add), that "nothing" nearly always means "something", especially when "nothing" is said in a non-normal tone of voice, or if its accompanied by a scowl or frown on the face.

Why do people do that? Why say its "nothing" when there is obviously "something"? I don't understand, i never have, and i still don't. When i'm troubled, i'll say so. If i'm upset with you and you ask me whether i am or not, i'll tell you that i am. If there really is nothing, i'll say so too but mostly people believe me when i say "nothing" because i say it like i mean it (which of course i do, because there is "nothing" wrong).

This is, without a doubt, another * sigh * moment. All-together now: * sigh *.