Confuse between Want and Don't want?

Am not sure whether you understand what is "want" and what is "don't want" or you just want to make daddy and mummy confuse.

To some extent, you can clearly tell me what you want and what you don't want. However, sometimes, when i asked you whether you want "something"(for eg, milk, bed time song, bedtime story...), you tend to tell me "don't want!". But, after a while, you will look for it.

Yesterday night, when we were in the room, daddy asked whether do you want the milk by holding the milk bottle in front of you, you told him "don't want", then daddy pretend to drink the milk, and you make some fuss, asking daddy to pass the milk bottle to you. And this morning, when you wake up, mummy asked whether do you want to have biscuit, happily you nod your head and said "want". Daddy gave me a blank look when i told him you said "want" biscuit! He also confused!

So now, daddy and mummy confused. Do you really understand "want" and "don't want" ?????
Or you just try to test on daddy and mummy's understanding of "want" and "don't want????