where did I go wrong?

I've noticed lately that having a conversation with my three year old often ends with me cowering fearfully behind a shield of silence. When did this happen? We used to have really great conversations like:
"Hi Mama!"
"Hi sweetie pie, did you have a good day at Gail's?"
"yeah"
"Did you eat?"
"Yes, I did."
"What did you eat?"
"I ate milk."
Then we sweetly hug and I kiss him on the cheek.

Now, our conversations are something like this:
"Mama, the sky is BLUUUEEE!"
"Yes, it is! And look at the white clouds!"
"No! NOO! NOOOHOHOHOHOHO...THERE AREN'T CLOUDS!", followed by several moments of screaming and crying uncontrollably. Suddenly I'm really appreciative of the car seat straps containing him.
"Yes, I think there are some white clouds. Can you see them out your window?"
"NO! You CAN'T say that! GO AWAY!"

And then I slink down in my driver's seat wondering "What the hell just happened?" Was this supposed to be a "rhetorical statement"? Am I missing something here? Three is just so much fun.