I'm not sure if this will be reassuring, but you are not alone.
It is very common to be overly anxious when pregnant after a miscarriage.
I am currently 30 weeks pregnant after a miscarriage of my last pregnancy at almost 13 weeks.
All I can say is that it will be a while before your anxiety and worry reduces.
I thought I would maybe worry less when I saw a heartbeat at a 6 week reassurance scan, but didn't.
I thought I would maybe worry less after my 12 week dating scan, but didn't.
I thought I would maybe worry less after I passed the 13 week mark (when I previously MC), but didn't.
I thought I would maybe worry less after the 20 week scan, but didn't.
When I did finally worry less and start to truly accept I was pregnant was when the baby started moving, which was around 23 weeks for regular movements. The constant, daily reassurance that all is well makes a huge difference.
All I can suggest to you for now is to do what works for you to reduce your worry. For me, I tried best I could to not think about being pregnant. I did all the essential things you have to do to look after yourself when pregnant, but aside from that I tried to block out the fact that I was pregnant and to do my best not to think about it. That was the only thing that worked for me to stop going out of my mind with worry for the first 5 plus months.
Good luck, and congratulations !