6 weeks 1 day- no heartbeat

Ashley
Has this happened to anyone? I went for my first ultrasound today and they measured me at 6 weeks 1 day. They saw the sac and the baby but couldn't detect a heartbeat. Has this happened to anyone? They want me to go back in a week to check again and I am trying not to freak out but finding it difficult not to. Trying to think postive! Thanks in advance for anyone's input.