thanks amanda! it turned out okay (aka, there was no break-in, i wasn't hurt, etc.) it was most likely as toby said, the guy who lives upstairs.
however, the police never showed up! they said they would send a car over (TWICE) and then never did. i called them to complain, but i didn't want to get yelled at for the FIFTH time. they yelled at me for not having called the local police station, and not 911, but if they tell me that they're sending out someone (twice) then they should. i can't believe they blamed their own failure to show up on ME.
ridiculous.