Internal ultrasound experiences?

I am due to have an internal ultrasound on 11th March as they are looking to see if I might have PCOS. I was quite saddened by the prospect as I thought my 1st ultrasound would be because I have a baby in there, not to see why I haven't. However I felt slightly better that it isn't going to be a gell on the tummy one! BUT I have no idea what it is going to be like. Has anyone had this? What are your experiences? My cycles are anything from 40 to 80 days so I personally think PCOS is likely. What happens during this kind of examination?