Oh hun no wonder you can't relax.

You have been through a hell of a lot, I think it's understandable you feel this way as all your past experiences have been so heartbreaking.
After my first loss I spoke to a very good friend that said this.
A mc is one of the worst things to ever happen to a woman and of course you're thinking back to when it happened before. A really good tip I was told and will try this time(Cos it will work) is to try and remember all the good feelings you felt about being pg and almost give permission for this little baby to stay with you. Bit arty farty but it sounds pretty cool to me..if you really think about it you don't have any control from now as to the outcome, its more than likely going to work for you, just think of little ducklings trying to get out of the water..Sounds bizarre but if it doesn't happen immediately they just keep trying and trying and trying til they do..and they always do!
I tried it with my second and third pg's, I felt so much better for enjoying the time I had with our babies even when I lost our second LO. Don't get me wrong, I did have moments of sheer terror when I thought everything was going wrong again but on the whole I felt a lot better.
I'm not sure how you manage the scan thing, I think that is the one thing that you will always dread and everyone I know that has had bad scans always says the same.
I hope writing your feelings down has made you feel a little better.
Good luck with your scan.
xxx