The only parts I know is :

I am sitting in a window

Then:

Singing Do do do do, do do do do, do do do do, do do do do.

I know the do's don't help. It's been driving me nuts for the last 3 days... very catchy song.

Are you thinking of "Tom's Diner" by Suzanne Vega?

SUZANNE VEGA LYRICS - Tom's Diner

Yes! Thank you so much!