Nightmare

I am 7 weeks pregnant measuring at 6 weeks. I don’t have any kids but i have 4 angel babies. I have a ultrasound this morning and I’m so nervous I had a nightmare. I dreamed I saw my baby on the ultrasound and it’s umbilical cord had been broke in two locations. How do you stop worrying after so many miscarriages? I know the nightmare came from worrying but how do you not worry? It was horrible and now I’m trying to go back to sleep but I’m scared I’m going to have a nightmare again :(