Hi OP, I'm a fellow anxious person! Like you it's always been a thing in my life but I had it relatively under control before PG. I haven't found a magic wand but a few things that have helped me:
1 - the stuff that helped me before. This is mainly getting outdoors, especially somewhere green at least every other day.
2 - distraction. Once I am thinking about something that makes me worry my mind will keep going back there. So I do puzzles or play a computer game or get the guitar out. It has to be something that needs some concentration and will distract my thought process for long enough. This is not the time for meditation or knitting for me!
3 - counselling. It helps me to have someone to talk to that I can share all my silly and not silly worries with and work out which ones are really the problem and whether I could/should do anything about it. Sometimes just saying it out loud helps me put it in perspective. I pay privately but you can access via GP as well.
4 - asking for help from GP/MW. Although I started on the normal path I have had more check ups and scans than are NHS recommended from 12 weeks. It helps reassure me and keep me calm.
5 - time. It has got easier as I have got further into the PG. I have had 2 losses before this so I was constantly afraid the baby would die. It didn't help that I was incredibly anxious in my 1st PG and "proved right". I also blamed my anxiety for my loss. I've had just as much anxiety this PG if not more and baby is fine. I still get a feeling of anxious dread sometimes but far less often now he's kicking me every day.
Good luck. Try different things and don't be too hard on yourself. Pregnancy is tough but you'll get through it!