Nothing's wrong

"Nothing's wrong!"
"Are you sure?" He stares at you. "There's something bothering you, I can tell!"
"I'm fine Ross, really!"
Ross looks at you in disbelif but nods and lets it go.
"So... Where's Monica?" Ross asks to break the silence.
"Oh, I think she went shopping with Pheebs."
"And you didn't go? What's wrong? If you don't go shopping, something must be wrong!"
You pause then say:

"I'm telling you Ross, nothings wrong!"
"I don't know how to tell you this, but..."