First off I think the tech would have said thats a big baby if it was measuring big, and second mine was 13 ounces and we were told he was long and skinny! LOL, So i would relax and ask your doc at the next appt., I'm sure he's not too big, plus ultrasounds are only estimations, they don't know for sure!!
Keep that in mind and good luck! Keep us posted on what your doc says!!