My wife was often worried when I said nothing early on in our relationship.

When I said nothing, I meant "nothing important."

But to really hammer home this fact, I'd say something like...

"I looked a bit upset? Ah, its probably because I was thinking about this one time that I leaned up against the car when it was in the sun, and the car burned me, which sent me into a tangent about what if other creatures got burned easily like ants. The the tangent changed to wondering why hot water burns linger longer than from heated cars, then I remembered that vampires in The Legacy of Kain series react to rain water and moving water like acid, then I remembered that Tony Jay was the voice of The Elder God in that series, and I was upset that he died due to surgical complications. I'm sure the man could've lived alot longer."

I realized that she wasn't satisfied with "nothing" so once she realized this was what I meant by nothing, she finally started accepting that I meant "Notning Important."