Dear NT:
You wrote:
> You wouldn’t know it by me.
>
> Does this sentence mean:
> 1-I won’t tell you although I know.
> 2-I wouldn’t tell you even if I knew.
> 3-I won’t tell you because I don’t know.
> or could it mean any of the above depending on the context?
>
This is a colloquial expression. It basically means “I have no means of knowing.” It is closer to #3.