Not a bit
Definition 1 of 1
Pro Tip 1/3Stress and Intonation
Emphasize 'not a bit' when speaking to make your lack of interest or surprise clear. 
He was expecting me to be grateful, but I was not a bit thankful for his 'help'.
Pro Tip 2/3Informal Situations
Use 'not a bit' in casual or informal conversations rather than in formal writing. 
You think I'm worried, but I'm not a bit concerned.
Pro Tip 3/3Understatement
'Not a bit' can be an understatement, hinting that something is actually significant. 
Am I upset about the game results? Not a bit — I'm actually devastated.