hello Loubylou
I think what you are feeling is natural, just try to fill your time from now until Saturday with activities you will enjoy, and that might take your mind off it a bit.
To be honest, I was in a big state for my 12 week scan in my second pregnancy, partly because I knew of a colleague who had a missed miscarriage - the baby had died early on, there was no sign of anything wrong. And then would you believe it, it happened to me to.It was very sad, heartbreakingly so, but at least I knew this could happen. On the one hand, I was prepared - unlike my friend who had no idea that such a thing could happen, and was really really shocked and traumatised- but it did teach me that you can worry your head off and if something is going to happen, it does, no matter how much you worry - the least you can do is try to enjoy life. On a happier note, I got pregnant again quickly, and had a great 12 week scan a few weeks ago.
These worries are all part of being a mum as Lucy5 says - the worries are so often outweighed by the joys, but both are pretty intense.
So fill your time, and good luck and good courage for saturday - let us know how it went! we'll look out for you