Is laughing at God, doubting Him?

"oh, yes you did" Genesis 21:6 "God has brought me laughter, and everyone who hears about this will laugh with me." Too often, I laugh at God and say, "yeah right, no way!" Sarah, standing in the doorway eavesdropping over the angel of the Lord and Abraham...abnd she laughed as well..."Why'd you laugh"? She said, "Oh, I didn't laugh". "Oh yes, you did". How fitting, the child be named Laughter when he was born.