I've had two miscarriages (July 2016 and March 2017). We found out it they could have been caused by a thyroid condition that I am now on medication for. I am 7 weeks today and had my first ultrasound. The heartbeat was 128 which was reassuring as we had never seen a heartbeat in previous pregnancies. The baby was only measuring 6 weeks 1 day. Should I be worried? I know I should be 7 weeks as I had used a OPK and ovulated on or near August 6th. My periods are regular too.