Amy Winehouse - what??!

Ok... so just one of the songs I was listening to today was "Back to Black". What is she going on about when she says "And life is like a pie (pipe?) and I'm a tiny penny rolling up the walls inside." Is this some cool drug reference that I'm too uncool to understand? I like to think she's saying "pie" because it reminds me of blackbirds baked in a pie, and pennies that were put in plum puddings for christmas. But I'm guessing it's pipe and I will be disappointed...