Getting Nervous as I approach week 7...

I've had 3 misscariges. March 2017 at 6 weeks 6 days. April 2018 at 5 weeks 5 days, and Aug 2018 at 6 weeks 5 days.

I'm now 6 weeks 4 days....I'm getting nervous as I'm approaching the time frame of my two misscariges..I heard when hearing a heartbeat rate goes to 10 percent of one...But I heard the heart beat and misscarried both anyways. I heard this babys heartbeat at 5 weeks 5 days...And I have a ultrasound this Monday at 7 weeks 1 day. I'm so scared.