how far along am I anyway?

So, I had my monthly doctor's appointment yesterday. Everything went great, but I'm just so confused on how far along I am! My original due date was November 25th, but after the first ultrasound they bumped it back to December 5th. Well, of course my chart still said the 25th and they congratulated me on making it through my first trimester (which I haven't). So, of course I questioned it and he's like "oh, well then, not quite but close." Anyway, he attempted to find the heartbeat with the doppler but didn't have much success. I have to laugh though because he tried for maybe 10 seconds before giving up. "Well, let's just do a quick ultrasound, " he says. Ha! So, we march down to the ultrasound room and I get settled there. Even though I knew everything was fine, I'll admit that I had a moment of paranoia before seeing the little heartbeat on the screen. What if something had happened in the past month? Everything was great though. Heart rate was 151 bpm and the baby measured at 11 weeks, thus confusing my due date even more (I thought I was 10 weeks, 3 days). The doctor said we'll leave it at the 5th though until my big 20 week ultrasound. So, right now I have like a 10-11 day due date window. LOL. I'm just glad everything is okay though.