I am gonna jump in and answer you too!!!

We had a transvag u/s at 8wks2d and the tech did move the probe around a lot, but for several reasons- I have a tilted uterus so it takes a minute to get the probe in the right place AND I specifically asked her to look at my left ovary because I had recently had some pretty sharp pain there and wanted to see if there was any sign of a cyst. I also asked if there was only one and she was certain that there wasn't another one in there
When I had DS I had a transvag because I was still nursing when I got pg with him (no period-no way to date pg). It was very fast and I don't remember being in the room for more than a few minutes- they didn't do anything but check the HB and measure to see how far along I was.
Don't worry, if the worst that happens is that you are blessed with twins it will one day be the best thing that ever happened to you!!! Speaking as a BTDT mom with "Irish twins" (mine are 14 months apart) the hardest part was not having a 1yr old and a newborn- newborns have a wonderful way of staying exactly where you leave them

The hard part was having a 1yr old and a 2yr old AT THE SAME TIME!!! I don't think there is enough redbull in the world to keep up the energy level you need at that point!!!! Luckily it calms down. Don't get me wrong, I enjoyed every minute (I am a SAHM) but there were times it was pretty nerve wracking!!!! LOL I know everything will work out- twins or not!!!