What to expect at early scan?

I found out that iwas pregnant a few weeks ago but then after a couple of days I started bleeding. I went to the doctors and he phoned up the Early Pregnancy Unit and they have booked me in for a scan this Friday, when i should be 6 weeks. They said that they wouldn't e able to see anything until then. The doctor said to go with a full bladder but i would have thought they would do an internal scan with it being so early. Has anyone else been for an early scan and what do they do. With my daughter, everything was straightforward so i only had the 12 week and 20 week ultrasound. What do they do if it is an internal scan? Have to be honest, i am not looking forward to it!