French language Q&A Forum

Is there a difference in meaning between "J'ai été là pendant quarante-cinq minutes" vs. "J'étais là pendant quarante-cinq minutes"?  My inclination was to use passé composé because it was an action that happened and ended, but I see the latter sentence in the lesson example.  Can someone please explain the difference?

Lots of interesting idioms in this exercise like - "rien que d'y penser" and "sans que j'y puisse quoi que ce soit". 

I'm trying to break down "rien que d'y penser" into English.  Rien que = nothing that or nothing but.  De = I'm just starting to recognize that "de" often comes after "que" in certain phrases (Je dors plutot que de travailler).  Y penser = to think about it. 

I still don't see how sans que j'y puisse means I can't or I am not able.  What does "y" refer to?