Congratulations on your pregnancy 
You sound just like the way I was when expecting my DC3. It was a terrifying pregnancy. Numerous scans, problems with the baby etc etc.
When I was expecting DC4, I made a conscious decision that whilst I couldn't control the outcome of the pregnancy, I could control how I coped with it. We hired an independent midwife to come to the house and train us in self-hypnosis techniques. I can't recommend this highly enough. She came to the house 3 times and each time went through a different "script" with us, and left a CD which I listened to every day. The CDs are very relaxing and help you bond with your baby. My DH could always tell when I had listened to it as it really calmed me down. The 2nd and 3rd CDs instruct you in relaxation techniques for using during labour, which I found very helpful.
I also saw a homeopath and got some remedies to help with anxiety.
Towards the end of the pregnancy I had reflexology treatments which were very relaxing.
I'd like to have done some yoga but wasn't able to fit it in with family commitments.
I knew that I was kidding myself to think that I could keep myself detached from my baby. Even if I lost the baby I wanted to know that I'd given it as much love as I could for as long as the pregnancy lasted, whether that was a few weeks or the full 40 weeks. If a baby is going to have a very short life that ends in a m/c, then far better that it's a joyful time than a time of panic and distress. That's a gift you can give your baby.
The medical support I'd had with DC3 wasn't really directly about keeping the baby safe, but more about helping me cope, and I ended up becoming dependant on scans and check-ups. I'd be reassured to see a heartbeat, but by the time I was in the hospital car park I'd be thinking that the baby had died in the last 3 minutes. I'd then recover for a few days and then get more terrified in the days leading up to the next scan. With DC4 I declined all but the routine scans and refused to be a "case". "Keep your soft marker bollocks to yourself this time" were the instructions I gave to my consultant!
I really really hope your scan tomorrow goes well 