Any of you have fetal dopplers?

I had my first appt yesterday and got to see and hear baby's heartbeat. I'm 8 weeks 2 days. But now I'm back to where I was when pg with dd and want to check hb occasionally for piece of mind. Mostly because I have no symptoms and it's worries me. Of you that have fetal dopplers how early did you start using them and find a hb? I think I'm still too early, was thinking maybe in a week I'd try but I'm just so much more anxious about this pg not working out for some reason even though my chance of miscarry is now like 2%