Don't worry, it's normal to feel anxious. I haven't slept properly at all, and I've got another day til my scan. i'm shattered from worrying lol
With my first the scan took about 30-40 mins, they have to take measurements etc which can either be quick or slow depending how active baby is.
I never had bloods taken at hospital, only ever my a community midwife at booking in, and bit late on in pregnancy.
Yes, you need to have a full bladder, sometimes it's too full though and they get you to pee... which is heaven lol
Good luck hun, will be thinking of you and looking forward to seeing pictures xx