i've had this with every ultrasound i've had! at 6.6, 7, 8, 12, and 20 weeks. lol
they ask u to undress from the waist down and put a big sheet over ur lower half..they do the external ultrasound first..the wand on the belly thing (only at my 8, 12 ,and 20 week u/s they did this, the first two were only internal cuz bubs was too small to see from the outside!)..and then at the end they did the internal which..to be completely blunt..pretty much looks like a medium sided dildo that they put a condom on and put a ton of lube on..and they stick like..a 1/4 of the length in, it doesnt hurt tho, they push on ur belly and ask u to push like you're having a bm in order to make sure your cervix stays closed when pressure is put on it, either having a bm or the pressure bubs puts on it. the internal for me at the last 3 appointments was like..30 seconds they stick it in move it around ask u to push and then take it out and thats it.
the first two where they only did the internal was about 5 minutes they looked to find the baby, moved the wand around a bit to get a good viewed, measured his length, found and measured his heartbeat, checked my cervix and that was it.. it was not as bad as it sounds just relax if you tense up it may be more uncomfortable
good luck