When I'm in a discussion with someone and then someone interrupts us and then I forgot what I said and want to continue from the point where I stopped, is it correct to say: 

> 
> What was I saying? 
> 
> 
> 

or is it: 

> 
> What did I say?
> 
> 
> 

And does this work in the second person, as well? For example, if I forgot what the person who was with me said, can I say: 

> 
> What were you saying? 
> 
> 
> 

or is it:

> 
> What did you say? 
> 
> 
>