Same chord progression through the whole song:
in this order G-C-G-C-Am-C-G-C-G

The picking rhythm is very upbeat, it sounds way better tuned down a half step but 
standard is fine too. 


                        G
When your dad left your mom
                   C
you moved into the condo
                          G
stayed there while he was gone
                           C
We stayed up late watching cable
                 Am
And we swam in the pool
                C
We ate all his food
                 G
Yeah we had so much fun
           C            G
When your dad left your mom


                        G
When your dad left your mom
                     C
She had to sell the house
                        G
We stayed up all night long
                          C
helping her move everything out
                         Am
In your empty bedroom upstairs
                             C 
You kissed me like you didn't care
                               G
Hey what else could possibly go wrong?
          C              G
When your dad left your mom


When your dad left your mom
Your little brother stayed with us
We helped him get his homework done
We got him up and ready for the bus
It was just for a few days
While your mom moved into the new place
And did what had to get done
When your dad left your mom

When your dad left your mom
You'd get so quiet sometimes
You'd say that nothing was wrong
Like I couldn't see it in your eyes
But every once in a while
I could still get you to smile
And I wrote you this stupid song
When your dad left your mom