cannot stop worrying

so I'm 26 weeks +3 and cannot stop worrying that I am going to lose my baby boy. This is my 1st baby and really trying to enjoy my pregnancy but everyday I wake up and the worry comes back. nothing has happened to make me think this none of my family or friends have suffered this. I had a worry the other day when I wasn't feeling him move as much but went straight to be seen and they checked his heart and they said he was fine but even a day later I was back worrying again. I really don't no what to do so any advice etc would be a great help thank you x