Advice for anxiety

I've just found out I'm pregnant with my first baby. I'm 4 weeks and 4 days. I had a chemical pregnancy in July and I'm so anxious that this one will end in a miscarriage. Any advice on how to stay calm? Was not going to tell any of my friends until I'm a bit further along but wondering if I should so I have someone to talk to? My husband is sympathetic but not sure her understands!