Vaginal ultrasound UPDATED

So I'm about to be 15 and I have recently been having some period problems. My doctor told me to have a normal ultrasound and a vaginal ultrasound to make sure everything is ok. My appointment is tomorrow and I am really nervous. What should I expect?

I wasn't as nervous as I thought I would be, thanks sooo much to you guys.

So I went there and she started the regular ultrasound but my bladder wasn't full enough. She had me drink water while she helped another patient. Once I got back into the room she did the ultra sound. She said she could see enough that I wouldn't have to do the vaginal ultrasound. I was relieved.